Surgical Pathology Case Study: A 6 Year Old Patient with Sudden Onset Abdominal Pain and a Worrisome Mass on Imaging

Case History

The patient is a 6 year old who developed abdominal pain 2 days prior to admission. The patient was in school when the abdominal pain began, resulting in the patient doubling over in pain. The pain resolved within 1 hour, however, because the initial presentation was an unremitting abdominal pain, the patient was taken to an outside hospital for evaluation. There was no vomiting, diarrhea, or constipation. On physical exam, the patient was very tender to palpation in the right lower quadrant and was unable to tolerate deep palpation. A computed tomography scan was subsequently ordered which showed a large mass in the pelvic peritoneum. The patient was admitted to surgery for an exploratory laparotomy, with resection of the pelvic mass.

Diagnosis

Received fresh in the Surgical Pathology laboratory is a 162.5 gm, 10.2 x 7.5 x 4.0 cm lobulated, ovoid mass of pink-tan, rubbery tissue that appears encapsulated by a thin translucent membrane. The margins are inked black and the specimen is serially sectioned revealing glistening, gray-tan soft tissue with focal areas of yellow discoloration and softening. Along one edge of the specimen, there is a 4.0 x 1.5 cm rim of dark red-brown, rubbery tissue (Figure 1). Portions of the fresh specimen are submitted in glutaraldehyde for electron microscopy if needed, RPMI for cytogenetics, and are snap-frozen as well. Touch preparations are also made and gross photographs are taken. Representative sections are submitted as follows:

Cassette 1-7:    Sections of mass including inked capsule

Cassette 8-10:   Representative sections from central portion of mass including areas of softening and discoloration

Cassette 11-13: Additional representative sections of the mass

Image 1. Cut surface of a gray-tan mass with yellow areas of discoloration and hemorrhage around periphery.

Histologically, the mass is composed of sheets and nests of small round cells along thin fibrous septa, giant multinucleated cells, and rare strap cells. Necrosis less than 5%. The margins are positive, although the specimen is unoriented. Venous and lymphatic invasion is absent. Immunohistochemical (IHC) stains are ordered and the results are listed below:

Positive IHC stains: Myogenin, desmin, CD56 and Bcl-2

Negative IHC stains: S-100, keratin AE1/AE3, CAM 5.2, SMA, CD99, Fli-1, WT-1, and EMA

In addition to the IHC stains, a portion of tissue was sent for cytogenetics testing, which showed a chromosomal translocation at t(2;13)(q35;q14). Based on the histologic appearance, IHC stains, and cytogenetic testing, the specimen was signed out as an alveolar rhabdomyosarcoma with a pathologic stageof pT2b, N0, MX.

Following the diagnosis, the patient was placed on a chemotherapy regimen of Vincristine, Adriamycin, Etoposide and Cytoxan, as well as radiation therapy.

Discussion

Rhabdomyosarcoma is the most common malignant soft tissue tumor in children and is the most common malignant solid tumor in children after neuroblastoma and Wilms tumor, accounting for 5-10% of all childhood tumors. 90% of these tumors occur in patients under the age of 25, and approximately 70% occur in children under 10 years of age. The most common locations of rhabdomyosarcoma are in the head and neck region, followed by the genitourinary system, extremities and then torso.

The 2013 World Health Organization classification of skeletal muscle tumors divided rhabdomyosarcoma into four types based on histology:

  1. Embryonal rhabdomyosarcoma (botryoides and anaplastic variant)
  2. Alveolar rhabdomyosarcoma (solid and anaplastic variant)
  3. Pleomorphic rhabdomyosarcoma
  4. Spindle cell/sclerosing rhabdomyosarcoma

Alveolar rhabdomyosarcoma (ARMS) accounts for approximately 20-30% of all rhabdomyosarcoma tumors, with no genetic predisposition. Although it is most common in teenagers, ARMS affects all ages. Most patients will present with a painless soft tissue mass, but based on the size and location of the mass, it may cause mass effect. A quarter of patients will have metastasis at the time of diagnosis, most commonly to the bone marrow, bones, and lymph nodes.

Grossly, ARMS presents as a solid, well-defined mass with a fleshy, tan-gray cut surface. Histologically, it is composed of small, blue, round cells and occasional round to spindle shaped rhabdomyoblasts. When compared to embryonal rhabdomyosarcoma, the rhabdomyoblasts in ARMS are slightly larger. ARMS is broken down into two subtypes: the classic subtype and the solid subtype. In the classic subtype, the tumor is composed of nests of cells that adhere to the edges of fibrous septa, resembling pulmonary alveoli (hence the name alveolar rhabdomyosarcoma). Multinucleated giant cells with a peripherally located nuclei may also be present. In the solid subtype, there will be nests and sheets of neoplastic cells that are separated by thin fibrovascular septa, but will not form in the classic alveolar pattern (Image 2).

Image 2. 20x photomicrograph demonstrating the neoplastic cells lining up along thin fibrous septa, giving the appearance of pulmonary alveoli

Due to the various appearances of rhabdomyosarcoma, it has become important to integrate immunohistochemical (IHC) stains and molecular testing into the diagnosis. The most common IHC stains that are used to determine the rhabdomyoblastic differentiation of a sarcoma is through the use of Myogenin and Myogenic differentiation 1 (MyoD1) stains, in which both stains will be positive in rhabdomyosarcoma. These two stains can be furthered used to help narrow down a diagnosis of ARMS because if more than 50% of the neoplastic cells express Myogenin, this is highly suggestive of a diagnosis of ARMS (Figure 3). In ARMS, the MyoD1 will have a variable expression. Additional positive IHC stains for ARMS can include: desmin, P-cadherin, and bcl-2.

Image 3. Myogenin IHC stain demonstrating a strong, homogenous expression

To go along with IHC stains, molecular testing has been shown to be affective with determining the type of rhabdomyosarcoma. There have been two translocations that have been identified in ARMS. The first is at t(2;13)(q35;q14), which results in a fusion of the PAX3 gene with the FOXO1 gene (previously known as the FKHR gene). This translocation is present in 60% of all ARMS cases, and has been found to occur mostly in older children and younger adults. The second translocation is at t(1;13)(p36;q14), which results in a fusion of the PAX7 gene with FOXO1, and is present in approximately 20% of all ARMS cases. The remaining 20% are fusion negative, and are associated with the solid subtype histologically. There is early preliminary data that shows a less aggressive disease course in patients with the PAX7-FOXO1 fusion, compared to those with the PAX3-FOXO1 fusion.

In order to determine the best treatment course, patients who are diagnosed with rhabdomyosarcoma are divided into a low risk, intermediate risk or high risk group based on the pathologic stage, clinical stage and clinical group. The pathologic stage is determined using the Pretreatment TNM Staging System that was set forth by the Intergroup Rhabdomyosarcoma Study (IRS) group (not the same as the TNM staging system put out by the American Joint Committee on Cancer) below:

The clinical stage is then determined using the TNM staging above and the Pretreatment Clinical Staging System below that is also put out by the IRS group:

In the above Clinical Staging System, a favorable site is defined as occurring in the orbit, biliary tract, head and neck region (excluding parameningeal) and genitourinary region (excluding prostate and bladder). Any other site not listed is considered unfavorable. Next, a clinical group is assigned based on the extent of the disease using the Clinical Grouping System below, which again is put out by the IRS group:

Lastly, based on the clinical stage and clinical group determined above, the patient is assigned a risk group of either low risk, intermediate risk, or high risk using the Children’s Oncology Group guidelines listed below:

When compared to embryonal rhabdomyosarcoma, which is the most common type of rhabdomyosarcoma, ARMS has a worst prognosis. The IRS group clinical group and stage can help to predict the overall outcome of the patient, with the standard treatment regimen composed of surgery, radiation therapy and chemotherapy.

References

  1. Dziuba I, Kurzawa P, Dopierala M, Larque A, Januszkiewicz-Lewandowska D. Rhabdomyosarcoma in Children – Current Pathologic and Molecular Classification. Pol J Pathol. 2018;69(1):20-32. doi:10.5114/pjp.2018.75333
  2. Liu H, Zhao W, Huang M, Zhou X, Gong Y, Lu Y. Alveolar rhabdomyosarcoma of nasopharynx and paranasal sinuses with metastasis to breast in a middle-aged woman: a case report and literature review. Int J Clin Exp Pathol. 2015;8(11):15316–15321. Published 2015 Nov 1.
  3. Owosho AA B Ch D, Huang SC Md, Chen S Mbbs, et al. A clinicopathologic study of head and neck rhabdomyosarcomas showing FOXO1 fusion-positive alveolar and MYOD1-mutant sclerosing are associated with unfavorable outcome. Oral Oncol. 2016;61:89–97. doi:10.1016/j.oraloncology.2016.08.017
  4. Ozer E. Alveolar Rhabdomyosarcoma. Pathology Outlines. http://www.pathologyoutlines.com/topic/softtissuealvrhabdo.html. Revised March 26, 2019. Accessed July 26, 2019.
  5. Rudzinski ER, Anderson JR, Hawkins DS, Skapek SX, Parham DM, Teot LA. The World Health Organization Classification of Skeletal Muscle Tumors in Pediatric Rhabdomyosarcoma: A Report From the Children’s Oncology Group. Arch Pathol Lab Med. 2015;139(10):1281–1287. doi:10.5858/arpa.2014-0475-OA
  6. Rhabdomyosarcoma Staging and Clinical Risk Groups. Stanford Medicine Surgical Pathology Criteria. http://surgpathcriteria.stanford.edu/srbc/rhabdomyosarcoma/staging.html. Accessed August 10, 2019

-Cory Nash is a board certified Pathologists’ Assistant, specializing in surgical and gross pathology. He currently works as a Pathologists’ Assistant at the University of Chicago Medical Center. His job involves the macroscopic examination, dissection and tissue submission of surgical specimens, ranging from biopsies to multi-organ resections. Cory has a special interest in head and neck pathology, as well as bone and soft tissue pathology. Cory can be followed on twitter at @iplaywithorgans.

Surgical Pathology Case Study: A 43 Year Old Female with a Lung Nodule Noted on Imaging Following Chest Congestion

Case History

The patient is a 43 year old woman who experienced chest congestion and presented to her local physicians office. A chest X-ray was ordered and demonstrated a lung abnormality. A follow-up CT scan confirmed a 1.9 cm smoothly marginated nodule in the upper lobe with no adenopathy and a normal liver and adrenal glands. The nodule was mildly hypermetabolic on PET scan. A bronchoscopy was performed, which was non-diagnostic. Two subsequent CT scans demonstrated no change in the size of the nodule. Overall, the patient feels well and denies cough, hemoptysis, dyspnea on exertion, and weight loss. Due to the suspicion of cancer, the patient has decided to undergo a lung lobectomy.

Diagnosis

Received in the Surgical Pathology lab for intraoperative consultation is a 30.0 x 7.2 x 2.2 cm lung lobectomy specimen. There is an attached 6.2 cm staple line, which is removed and the subjacent resection margin is inked blue. The entire pleural surface is inked black. The specimen is sectioned revealing a 2.1 x 1.7 x 1.0 cm white-tan, firm, round nodule that is 0.5 cm from the blue inked resection margin and 0.2 cm from the black inked pleural surface. The remainder of the specimen is composed of red-tan, spongy, grossly unremarkable lung parenchyma without nodules or other lesions. Photographs of the specimen are taken (Figure 1). A representative section of the nodule is submitted for frozen section and read out as “diagnosis deferred”. Representative sections of the specimen are submitted as follows:

A1FS:   Frozen section remnant

A2-A7:   Nodule, entirely submitted

A8-A10:   Grossly unremarkable lung parenchyma

Immunohistochemical stains show the epithelial cells in the lesion to be positive for CK7, TTF-1, and surfactant proteins A and B which supports these cells to be type 2 pneumocytes (all controls are appropriate). Based on the immunohistochemical stains and routine H&E slides, the case was signed out as a sclerosing pneumocytoma

Image 1. Gross presentation of the well-defined, round sclerosing pneumocytoma.

Discussion

Sclerosing pneumocytoma (SP) is a rare, benign pulmonary tumor that was first described in 1956 as a vascular tumor, but has since been found to be of primitive respiratory epithelium origin. In the past, SP has also been referred to as sclerosing hemangioma, pneumocytoma, and papillary pneumocytoma, but the 2015 World Health Organization classification of lung tumors states that the agreed upon term for this tumor should be a sclerosing pneumocytoma. SP is commonly seen in middle aged adults, with a female to male ratio of 5:1. There is no racial bias. Patients are usually asymptomatic, with the tumor incidentally found on screening chest radiographs. If the patient was to present with any symptoms, they would usually include a cough, hemoptysis and chest pain. Radiographically, SP appears as a solitary, well-defined, homogenous nodule along the periphery of the lung.

Grossly, most SPs appear as a solitary, firm, well-circumscribed, yellow-tan mass generally arising along the periphery of the lung. The majority of these tumors appear within the lung parenchyma, but there have been cases reported of endobronchial and pleural based SP tumors. Multifocal unilateral tumors and bilateral tumors are uncommon.

Histologically, SP consists of two epithelial cell types: surface cells and round cells. Surface cells are cuboidal, resembling type II pneumocytes, with finely stippled nuclear chromatin, indistinct nuclei, occasional nuclear grooves, and inclusions. The stromal round cells will have bland oval nuclei with coarse chromatin and eosinophilic cytoplasm (Figure 2). Both the surface cells and round cells will have a low mitotic rate, but can have moderate to marked nuclear atypia. Ciliated bronchial epithelium is often identified in the tumor. There are four architectural patterns identified within SP: papillary, sclerotic, solid and hemorrhagic, with over 90% of SPs displaying three of the patterns, and all of the tumors containing at least two of the patterns.

  • Papillary pattern: Complex papillae composed of surface cells covering a stroma of round cells
  • Sclerotic pattern: Papillae containing hyalinized collagen, either in solid areas or along the periphery of hemorrhagic areas (Figure 3)
  • Solid pattern: Sheets of round cells bordered by surface cells
  • Hemorrhagic pattern: Large blood filled spaces
Image 2. Photomicrograph demonstrating the cuboidal surface cells and round stromal cells.
Image 3. Photomicrograph of the papillary and sclerotic architectural patterns.

Immunohistochemical stains can be helpful in the diagnosis of SP, with both the surface cells and round cells exhibiting expression of thyroid transcription factor 1 (TTF-1) and epithelial membrane antigen (EMA). It should be noted that TTF-1 is also used for the diagnosis of pulmonary adenocarcinoma, increasing the risk of misdiagnosing SP. The surface cells will also express both pancytokeratin (AE1/AE3) and Napsin A, with the round cells being negative for AE1/AE3, but having a variable expression of cytokeratin 7 and the low molecular weight cytokeratin (CAM 5.2). Molecular pathology has demonstrated a frequent loss of heterozygosity at 5q, 10q and 9p, and an allelic loses at p16 in the surface and rounds cells. Although the immunohistochemical stains and molecular pathology results can be very helpful, diagnosis of a SP is still largely based on routine H&E slides showing the two epithelial cell types and four architectural patterns.

Electron microscopy will show abundant lamellar bodies similar to those in type II pneumocytes in the surface cells. Round cells will lack the lamellar bodies and instead will contain variably-sized electron-dense bodies that have been thought to represent the different stages of lamellar body maturation.

The differential diagnosis for SP includes a variety of benign and malignant neoplasms, which can be difficult to distinguish on cytology, small biopsies and intraoperative consultations. The cytologic features include moderate to high cellularity with a bloody background and foamy macrophages, occasional nuclear pleomorphism in the round cells, absent mitotic figures, and occasional necrosis with cholesterol clefts and calcifications. In the case of small biopsies, making a diagnosis of SP can be difficult if the papillary pattern is highly prevalent without one of the other three patterns present. With intraoperative consultations, the frozen section artifact can make it difficult to appreciate the two epithelial cell types or the four architectural patterns. The gross examination, as well as the radiographic findings of a well-circumscribed tumor can help point the Pathologist to favoring a benign neoplasm over a malignant one. The benign neoplasms that should be considered in the differential diagnosis include:

  • Clear cell tumor, which will have clear cells with scant stroma, thin-walled vessels and a strong expression of HMB-45
  • Pulmonary hamartoma, which will have a combination of cartilage, myxoid stroma, adipose tissue and trapped respiratory epithelium
  • Hemangiomas, which are rare in the lung, and will lack epithelial cells and contain either a cavernous or capillary morphology

The malignant neoplasms that should be considered in the differential diagnosis include:

  • Bronchioalveolar carcinoma, which can have a papillary pattern, but will not contain the two epithelial cell types and combination of the four architectural patterns
  • Metastatic papillary thyroid carcinoma, which is distinguished from SP by the presence of the characteristic Orphan Annie nuclei
  • Metastatic renal cell carcinoma, which will contain nuclear atypia and striking vascularity
  • Carcinoid, which will contain organoid and ribbon-like growth patterns

Currently, with the benign nature of SP, surgical excision is the preferred treatment choice to cure the patient. There have been cases reported of lymph node metastasis and recurrence, but neither of these appear to effect the prognosis. This just helps to highlight the need for a multidisciplinary approach to this benign tumor.

References

  1. Hisson E, Rao R. Pneumocytoma (sclerosing hemangioma), a Potential Pitfall. Diagn Cytopathol. 2017;45(8):744-749
  2. Keylock JB, Galvin JR, Franks TJ. Sclerosing Hemangioma of the Lung. Arch Pathol Lab Med. 2009;133(5):820-825.
  3. Travis WD, Brambilla E, Nicholson AG, et al. The 2015 World Health Organization Classification of Lung Tumors: Impact of Genetic, Clinical and Radiologic Advances Since the 2004 Classification. J Thorac Oncol. 2015;10(9):1243-1260.
  4. Wu R. Sclerosing Pneumocytoma (Sclerosing Hemangioma). Pathology Outlines. http://www.pathologyoutlines.com/topic/lungtumorsclerosingheman.html. Revised February 19, 2019. Accessed June 6, 2019.

-Cory Nash is a board certified Pathologists’ Assistant, specializing in surgical and gross pathology. He currently works as a Pathologists’ Assistant at the University of Chicago Medical Center. His job involves the macroscopic examination, dissection and tissue submission of surgical specimens, ranging from biopsies to multi-organ resections. Cory has a special interest in head and neck pathology, as well as bone and soft tissue pathology. Cory can be followed on twitter at @iplaywithorgans.

Surgical Pathology Case Study: A 3 Year Old Male with a Suspicious Lesion on Imaging Following an Injury

Case History

The patient is a 3 year old male with no significant past medical history who presented to the ED with left lower extremity pain for 24 hours after falling while playing with family members. The patient’s mother was present at bedside providing the history, but was not present at the time of the fall. It is unclear how the patient injured his ankle, but family members noticed the child grabbing his ankle and suspected that he may have twisted it. After the fall, the patient was unable/unwilling to ambulate on the ankle. There is no history of fractures or cancer.

An x-ray and subsequent MRI were ordered of the ankle which demonstrated an expansile lytic lesion involving the metaphysis of the distal tibia measuring approximately 3.4 x 2.2 cm (Figure 1 and 2). The margins of this lesion are indistinct, and there is cortical irregularity at the anterior and lateral aspect of the distal metaphysis of the tibia, likely representing a pathologic fracture. The differential diagnosis includes infection, aneurysmal bone cyst, nonossifying fibroma, osteoblastoma and histiocytosis.

The patient and family then followed up with Orthopedics, who proceeded to perform a biopsy of the lytic lesion in order to determine the nature of the lesion. The results are below.

Figure 1. Xray of the distal tibia demonstrating the lesion.
Figure 2. MRI demonstrating the lytic lesion involving the metaphysis of the distal tibia.

Diagnosis

Received fresh for intraoperative consultation is a 1.1 x 0.6 x 0.5 cm aggregate of white-tan soft tissue fragments. Half of the tissue fragments are frozen and read out as “spindle cell proliferation. Consideration of low-grade vasoformative lesion. Defer to permanent,” with 3 pathologists consulting on the diagnosis. The remainder of the tissue not submitted for frozen section, as well as the entirety of a second container from the same lesion, is submitted for routine processing.

On microscopy, the biopsies demonstrate a moderately cellular proliferation of fasciculated spindle cells in a collagenous to myxoid stroma. Nuclei are predominantly oval with variably fine to granular chromatin. Many cells have moderate amounts of tapering eosinophilic cytoplasm, resembling strap cells. Inflammatory cells and osteoclast-like giant cells are admixed (Figure 3 and 4). Immunohistochemical stains demonstrate lesional spindle cells to be positive for CD31, ERG, and FLI1. AE1/AE3 and CAM5.2 highlight rare lesional spindle cells. SMA stains some stellate spindle cells, favored to represent associated myofibroblasts. Desmin, MDM2, CDK4, ALK, and S100 are negative in plump lesional cells (Figure 5 and 6). Overall, the features are consistent with pseudomyogenic hemangioendothelioma, a rare vascular tumor. Although more commonly present in soft tissue, primary bone cases have been reported. These neoplasms have some risk for local recurrence, but only rarely distant metastasis. A portion of tissue was sent to the University of Nebraska Medical Center to evaluate for a characteristic gene rearrangement (SERPINE1-FOSB) that is present in at least a subset of pseudomyogenic hemangioendotheliomas. This was negative.

The lesion was then curettaged by the surgical team.The patient and his family had two follow up office visits with the Orthopedics department. The first one, a week after surgery, was unremarkable. The second visit, two weeks after surgery, was notable for the patient developing a cutaneous rash on both arms and chest. Due to literature citing that these tumors generally arise in the soft tissue, the clinician suggested that the patient and family follow up with pediatric dermatology to ensure that this new rash is not related to the pseudomyogenic hemangioendothelioma. Unfortunately due to insurance, the patient and family had to see a dermatologist at a different institution, and no further visits have taken place.

Figure 3. Photomicrograph of the strap-like cells with tapering eosinophilic cytoplasm , and osteoclast-like giant cells.
Figure 4. Higher power photomicrograph demonstrating the appearance of the strap-like cells with tapering eosinophilic cytoplasmFigure 4.

Discussion

Pseudomyogenic hemangioendothelioma (PHE) is a rare vascular tumor that most commonly arises in the skin and soft tissues of the extremities. It is usually multifocal, appearing in multiple tissue planes, such as the mucosa, dermis, subcutis and skeletal muscle, in a variety of different anatomic sites. Although even less common, PHE can also involve bone (such as this case). PHE has a male predilection, typically appearing in the second to fourth decades of life. Of the most common symptoms that the patient presents with, pain appears to top the list, although it should be stated that only about half of the patients experience pain.

Grossly, skin and soft tissue PHE tumors appear firm, ill-defined and gray-white. When they involve bone, they appear as multiple discrete, pink-tan to dark brown hemorrhagic tumors with surrounding sclerosis, ranging from 0.1 to 6.5 cm in greatest dimension.

Histologically, PHE demonstrates plump spindle and rhabdomyoblast-like cells with densely eosinophilic cytoplasm that grows in sheets and fascicles. The cells can be mistaken as rhabdomyoblasts because of the eosinophilic cytoplasm that pushes the nucleus to the periphery of the cell. Immunohistochemical studies are very helpful in order to determine a diagnosis of PHE. AE1/AE3, ERG, FLI-1 and CD31 are positive, whereas CD34, desmin and S100 are negative. Karyotyping has revealed a fusion of genes SERPINE1-FOSB that corresponds to the recurrent translocation t(7;19)(q22;q13). In this case, the SERPINE1-FOSBgene rearrangement was negative, but could possibly be due to a variant fusion gene.

Making a histologic diagnosis can be difficult for a Pathologist, due to the wide variety of differential diagnoses that will need to be excluded first.

The differential diagnosis for a cutaneous tumor includes:

  • Cellular benign fibrous histiocytoma (lacks rhabdomyoblast-like cells and neutrophilic infiltrates, contains mitotic figures, and is negative for cytokeratin and CD31)
  • Spindle cell squamous cell carcinoma (usually in sun-damaged skin, with nuclear atypia and negative endothelial markers)
  • Epithelioid sarcoma (negative INI1, positive EMA and CD34, and a nodular architecture with central necrosis and more nuclear atypia)

The differential diagnosis for soft tissue tumors include:

  • Epithelioid sarcoma (see above)
  • Epithelioid hemangioendothelioma (usually intracytoplasmic vacuoles, positive CD34 and CAMTA1, and a t(1;3)(p36.3;q25) translocation resulting in WWTR1-CAMTA1 gene fusion)
  • Epithelioid angiosarcoma (vasoformative architecture with sheet-like pattern, nuclear atypia, high nuclear grade, frequent mitosis and irregular vascular channels)

 The differential diagnosis for bone tumors includes:

  • Epithelioid hemangioma (lacks rhabdomyoblast-like cells)
  • Giant cell tumor (lacks rhabdomyoblast-like cells and fascicles of spindle cells)
  • Osteoblastoma (lacks rhabdomyoblast-like cells and fascicles of spindle cells)

In a study by Inyang et al, when PHE involved bone, imaging would demonstrate multiple to innumerable discontinuous tumors throughout the affected bone, involving the cortex and/or medullary cavity of the epiphysis, metaphysis, or diaphysis. On x-ray and computed tomography, the lesions appeared as well circumscribed, lobulated and lytic, with a sclerotic rim on some of the lesions. On magnetic resonance imaging, T1-weighted images would appear dark, and T2-weighted images would appear hyperintense.

PHE has a tendency to recur locally, but rarely develops distant metastases. Since PHE presents as a multifocal disease and can be easily confused for a distant metastasis, care needs to be taken to ensure that a diagnosis of PHE is not overlooked.

Surgical ablation and excision is the standard treatment for a patient with PHE, with a few cases noted of patients being treated with radiotherapy and/or adjuvant chemotherapy, in addition to surgery. Everolimus and sirolimus have recently been found to be effective in cases of patient with PHE that had metastatic and relapsing multifocal PHE.

Figure 5. Immunohistochemical stains (part 1 of 2)
Figure 6. Immunohistochemical stains (part 2 of 2)

References

  1. Hornick JL, Fletcher CDM. “Pseudomyogenic Hemangioendothelioma: A Distinctive, Often Multicentric Tumor With Indolent Behavior.” Am J Surg Pathol. 2011; 35: 190201.
  2. Inyang A, et al. “Primary Pseudomyogenic Hemangioendothelioma of Bone.” Am J Surg Pathol. 2016; 40: 587598.
  3. Pradhan D. “Pseudomyogenic hemangioendothelioma of skin, bone and soft tissue; a clinicopathological, immunohistochemical, and fluorescence in situ hybridization study.” Hum Pathol. 2018; 71: 126134.
  4. Sugita S, Hirano H, Kikuchi N, et al. Diagnostic utility of FOSB immunohistochemistry in pseudomyogenic hemangioendothelioma and its histological mimics. Diagn Pathol. 2016;11(1):75. Published 2016 Aug 11. doi:10.1186/s13000-016-0530-2

-Cory Nash is a board certified Pathologists’ Assistant, specializing in surgical and gross pathology. He currently works as a Pathologists’ Assistant at the University of Chicago Medical Center. His job involves the macroscopic examination, dissection and tissue submission of surgical specimens, ranging from biopsies to multi-organ resections. Cory has a special interest in head and neck pathology, as well as bone and soft tissue pathology. Cory can be followed on twitter at @iplaywithorgans.

Surgical Pathology Case Study: A 2.5 Year Old Male Who Presents with Jaundice and Pruritus

Case History

The patient is a 2.5 year old male who is being evaluated for a liver transplant versus biliary diversion surgery. The patient was born at 2 kilograms and went home with mom one week after birth. The patient was readmitted back to the hospital for evaluation of jaundice and since then the patient has been intermittently hospitalized for episodes of worsening jaundice, acholic stools, scleral icterus, and pruritus. At 5 months of age, the patient was diagnosed with progressive familial intrahepatic cholestasis, type 2, and was placed on the liver transplant list. As a result of the liver failure, the patient has developed coagulopathy, hypocalcemia resulting in seizures, and pruritus. The family history is significant for no known congenital liver diseases.

Table 1. Pertinent lab findings.

The father was worked up for living donation and was found to be a suitable donor, and is donating the left lateral segment of his liver.

Diagnosis

Received in the Surgical Pathology laboratory is a 700 gm, 23.5 x 14.5 x 3.5 cm explanted liver with an attached 4.5 x 1.2 x 0.4 cm gallbladder. The liver specimen has a smooth, green-red liver capsule without any grossly identifiable nodules or lesions (Image 1). The gallbladder has a yellow-pink external surface and is opened to reveal a 1.5 x 0.7 x 0.4 cm dark brown stone with a small amount of brown-yellow bile fluid. The liver is sectioned to reveal a smooth green-red cut surface (Image 2). No lesions are identified and minimal hilar structures are included with the specimen. Portions of the specimen have been taken for electron microscopy and frozen for future diagnostic purposes. Submitted sections include:

Cassette 1 and 2:   Hilar structures

Cassettes 3-15:   Representative sections of liver parenchyma

Cassette 16:   representative section of gallbladder

Image 1. Posterior aspect of green-tinged liver
Image 2. Cut section of liver

On microscopy, the trichrome stain highlights the presence of portal and centrilobular fibrosis, with focal bridging. However, regenerative nodule formation is not evident. The portal tracts contain sparse mononuclear cell infiltrates. Significant bile ductular proliferation is also evident, as confirmed by a CK7 immunostain. However, the native bile ducts appear unremarkable. There is also considerable hepatocellular and canalicular cholestasis in the centrilobular regions. Occasional multinucleated hepatocytes are also seen within the centrolobular zones. No steatosis is evident.

This constellation of histologic features is consistent with the clinical history of progressive familial intrahepatic cholestasis, type II.

Discussion

Progressive familial intrahepatic cholestasis (PFIC) is a group of autosomal recessive disorders that affects bile formation and results in cholestasis of the liver, usually beginning in infancy and childhood. There are three types of PFIC, each related to a mutation in the liver transport system genes that are involved in bile formation. PFIC type 1 (PFIC1), which is also referred to as Byler disease, is due to impaired bile salt secretion related to a ATP8B1 gene that encodes the FIC1 protein. PFIC type 2 (PFIC2), which is referred to as Byler syndrome, is due to impaired bile salt secretion (similar to type 1), but is related to the ABCB11 gene that encodes the bile salt export pump, or BSEP. PFIC type 3 (PFIC3) is due to impaired biliary phospholipid secretion that is related to a defect in the ABCB4 gene that encodes the multi-drug resistant 3 protein, or MDR3.

PFIC is suspected to be the cause of cholestasis in 10-15% of children, and is also the underlying cause of liver transplants in 10-15% of children. The exact prevalence remains unknown, but is estimated to be between 1 in every 50,000-100,000 births. PFIC1 and PFIC2 account for 2/3 of all PFIC cases, with PFIC3 making up the other 1/3. PFIC is present worldwide, and there does not appear to be a gender predilection.

The main clinical manifestation in all forms of PFIC, hence the name, is cholestasis, and will usually appear in the first few months of life with PFIC1 and PFIC2. Recurring episodes of jaundice are also present in PFIC1, whereas permanent jaundice and a rapid evolution to liver failure are characteristic of PFIC2. In PFIC3, cholestasis is noted within the first year of life in 1/3 of all cases, but rarely will be present in the neonatal period. PFIC3 can also present later in infancy, childhood or even early adulthood, with gastrointestinal bleeding due to portal hypertension and cirrhosis being the main symptoms that the patient would present with. Pruritus is severe in PFIC 1 and 2, but has a more mild presentation in PFIC3. There have been multiple cases reported of hepatocellular carcinoma that are associated with PFIC2, but there so far have not been any cases of hepatocellular carcinoma reported that are associated with PFIC3. Other signs and symptoms that may be present in PFIC1 include short stature, deafness, diarrhea, pancreatitis and liver steatosis. When examining clinical laboratory results, patients with PFIC1 and PFIC 2 will have normal serum gamma-glutamyltransferase (GGT) levels, but patients with PFIC3 will have elevated GGT levels. PFIC1 and PFIC2 can be differentiated from each other by the higher transaminase and alpha-fetoprotein levels that are found in PFIC2. When analyzing the biliary bile salt concentrations, PFIC1 will have mildly decreased levels (3-8 mM), PFIC2 will have drastically decreased levels (<1 mM), and PFIC3 will have normal levels. In addition, the biliary bile salt:phospholipid ratio and the cholesterol:phospholipid ratio will be approximately 5 times higher in PFIC3 than in normal bile, due to the biliary phospholipid levels being dramatically decreased (normal phospholipid range = 19-24%, PFIC phospholipid range = 1-15%).

Histologically, PFIC1 and PFIC 2 will have canalicular cholestasis, an absence of true ductular proliferation, and periportal biliary metaplasia of the hepatocytes. In PFIC2, these manifestations are much more worrisome with more marked lobular and portal fibrosis, and inflammation, as well as having much more pronounced necrosis and giant cell transformation (Images 3 and 4). PFIC3 will show portal fibrosis and true ductal proliferation, with a mixed inflammatory infiltrate. In addition, cholestasis can be present in the lobule and in some of the ductules that contain bile plugs. Cytokeratin staining can help confirm the ductular proliferation within the portal tract. Mild or absent canalicular staining with BSEP and MDR3 antibodies will help to diagnose PFIC2 and PFIC3, respectively.

Image 3. Photomicrograph demonstrating cholestasis, centrilobular necrosis, lobular inflammation, and giant cells (H&E)
Image 4. Photomicrograph demonstrating portal, centrilobular and bridging fibrosis (Trichrome)

A diagnosis of PFIC is based on the clinical manifestations, liver ultrasonography, cholangiography and liver histology, as well as on specific tests for excluding other causes of childhood cholestasis (such as biliary atresia, Alagille syndrome, cystic fibrosis and alpha-1 antitrypsine deficiency). Ultrasonography of the liver will be normal with the exception of a possible dilated gallbladder. At the time of the liver biopsy, a portion of tissue can be submitted for electron microscopy, which in the case of PFIC, can show canalicular dilatation, microvilli loss, abnormal mitochondrial internal structures, and varying intra-canalicular accumulations of bile. PFIC1 will have coarsely, granular bile on electron microscopy, whereas PFIC2 will have a more amorphous appearance. If biliary obstruction is noted on the liver biopsy, a cholangiography will need to be performed to exclude sclerosing cholangitis. If a normal biliary tree is observed, as in PFIC, bile can be collected for biliary bile salt analysis (which was discussed earlier in the laboratory results section). Differentiating between PFIC1, PFIC2 and PFIC3 can be quite troublesome, but luckily Davit-Spraul, Gonzales, Baussan and Jacquemin proposed a fantastic schematic for the clinical diagnosis of PFIC, which is presented as Figure 1.

Figure 1. Schematic proposed for the clinical diagnosis of progressive familial intrahepatic cholestasis

Ursodeoxycholic acid (UDCA) therapy should be considered in all patients with PFIC to prevent liver damage and provide relief from pruritus. Rifampicin and Cholestyramine can help in cases of PFIC3, but have been found to provide no improvement in PFIC1 or PFIC2. In some PFIC1 or PFIC2 patients, biliary diversion can also relieve pruritus and slow disease progression. The total caloric intake should be around 125% of the recommended daily allowance. Dietary fats should come in the form of medium chain triglycerides, and care should be taken to check the patient’s vitamin levels to look for signs of vitamin deficiency. Patients with PFIC2 should be monitored for hepatocellular carcinoma, beginning from the first year of life. Ultimately, most PFIC patients develop fibrosis and end-stage liver disease before adulthood, and are candidates for liver transplantation. Diarrhea, steatosis and short stature may not improve after liver transplantation, and could become aggravated from the procedure. Hepatocyte transplantation, gene therapy or specific targeted pharmacotherapy are possible alternative therapies for PFIC, but will require more research and studies to determine whether they are viable options.

References

  1. Davit-Spraul A, Gonzales E, Baussan C, Jacquemin E. Progressive familial intrahepatic cholestasis. Orphanet J Rare Dis. 2009;4(1). doi:10.1186/1750-1172-4-1
  2. Evason K, Bove KE, Finegold MJ, et al. Morphologic findings in progressive familial intrahepatic cholestasis 2 (PFIC2): correlation with genetic and immunohistochemical studies. Am J Surg Pathol. 2011;35(5):687–696. doi:10.1097/PAS.0b013e318212ec87
  3. Srivastava A. Progressive Familial Intrahepatic Cholestasis. J Clin Exp Hepatol. 2013;4(1):25-36. doi: 10.1016/j.jceh.2013.10.005

-Cory Nash is a board certified Pathologists’ Assistant, specializing in surgical and gross pathology. He currently works as a Pathologists’ Assistant at the University of Chicago Medical Center. His job involves the macroscopic examination, dissection and tissue submission of surgical specimens, ranging from biopsies to multi-organ resections. Cory has a special interest in head and neck pathology, as well as bone and soft tissue pathology. Cory can be followed on twitter at @iplaywithorgans.

Surgical Pathology Case Study: A 63 Year Old Male with a ~60 Year Recurring Neck Mass

Case History

A 63 year old man presented with a long standing history of a recurring pleomorphic adenoma of the parotid gland. As a child, the patient had radiotherapy to the bilateral parotid glands for parotid swelling. He then developed a left parotid mass ~15 years later and underwent parotidectomy. After another recurrence ~15 years after the initial parotidectomy, he underwent a second resection of multiple masses in the preauricular region. The patient then developed a recurrence ~20 years after the second resection and underwent neutron beam therapy. The patient tolerated the treatment well noting mild dry mouth, which is persistent, and left ear pain, but otherwise has no major long-term sequelae from the treatment. Eighteen years after the neutron beam therapy, the patient developed a left submandibular mass. A subsequent biopsy of the mass revealed a pleomorphic adenoma.  Enlarged left and right submental and submandibular nodes were noted, with biopsies performed at an outside hospital of these nodes demonstrating metastatic poorly differentiated carcinoma within three lymph nodes. It was noted on this pathology report that the histological features, in light of the history, could represent a carcinoma ex pleomorphic adenoma. A CT scan of the head and neck revealed a large multiloculated, cystic, rim-enhancing mass within the left parotid gland, as well as large enhancing lymph nodes within the right anterior and posterior cervical triangle and the right submandibular space, the largest of which measured 2.1 cm. A PET scan showed increased activity within the right neck. Upon meeting with otolaryngology, a 4.0 x 7.0 cm lobular, non-fixed left parotid mass, and two level 1B right sided nodes, were palpated. Based on the patient’s history, physical exam, and prior biopsy results, it was decided to proceed with a parotidectomy and bilateral neck dissection. 

Diagnosis

Received in the Surgical Pathology laboratory is a soft tissue mass resection from the area of the left parotid gland measuring 9.0 x 6.0 x 4.2 cm. The specimen is oriented by a single long stitch designating the superior aspect, and a double long stitch designating the lateral aspect (Figure 1). The specimen is entirely inked black, and then bisected to reveal multiple discrete, white-tan, partially cystic masses ranging in size from 0.2-4.0 cm in greatest dimension and measuring 7.0 x 3.5 x 3.0 cm in aggregate dimension (Figure 2). The largest mass is partially cystic with the cystic component measuring 1.2 cm in greatest dimension. This largest mass abuts the anterior, medial and lateral margins. The remaining tumor deposits are located:

– 1.2 cm from the inferior margin

– 0.4 cm from the superior margin

– 0.9 cm from the posterior margin

No gross salivary gland tissue is identified. The remainder of the specimen consists of unremarkable yellow adipose tissue and red-brown skeletal muscle. The specimen is submitted as follows.

Cassette 1:   superior margin

Cassette 2:   representative sections of anterior margin

Cassette 3:   anterior superior margin

Cassette 4:   anterior inferior margin

Cassette 5:   posterior margin

Cassette 6-9:   representative sections of mass with approach to lateral margin

Cassette 10:   representative sections of mass with approach to medial margin

Cassette 11:   mass in relation to surrounding skeletal muscle

Cassette12-15:   representative sections of mass

On microscopy, the specimen contains nests of tumor cells ranging in size from 0.2 to 4.0 cm within a dense fibrous matrix. Although these deposits may represent lymph node metastases, no residual lymphoid tissue is present. The tumor is represented by residual pleomorphic adenoma and numerous soft tissue deposits of pleomorphic adenoma (Figure 3). Admixed are broad areas of high grade carcinoma with necrosis (Figure 4). Most regions show adenocarcinoma, although a rare focus of squamous differentiation is also present. The lateral margin is positive for carcinoma, and a pleomorphic adenoma component approaches within 0.1 cm of the medial margin. The anterior, posterior, inferior, and superior margins are all free of tumor. No salivary gland tissue is identified.

In addition, eleven frozen sections are submitted from various areas surrounding the mass, with five of the eleven frozen sections demonstrating tumor deposits. A right neck dissection is performed with following results:

Level IB: 2 of 3 positive (largest deposit: 1.8 cm)

Level II and III: 1 of 14 positive, Level II (1.9cm)

Level IV: 1 of 8 positive (2.0 cm)

Based on these results, the specimen was signed out as carcinoma ex-pleomorphic adenoma, and designated as pT4aN2cMx

Figure 3. 2x photomicrograph showing a classic appearing pleomorphic adenoma with satellite nodules along the periphery

Discussion

Carcinoma ex pleomorphic adenoma (CXPA) is a carcinoma that arises in a primary (de novo) or recurrent benign pleomorphic adenoma (PA). While a PA is the most common salivary gland tumor, accounting for approximately 80% of all benign salivary gland tumors, a CXPA is quite uncommon, accounting for only 3.6% of all salivary gland tumors. CXPA is predominantly found in the sixth to eighth decades of life, with a slight predilection for females. CXPA arises most commonly in the salivary glands, in particular the parotid and the submandibular glands. CXPA can also arise in the minor salivary glands in the oral cavity, although these tumors tend to be smaller than their counterparts in the parotid and submandibular gland. There have also been cases of CXPA in the breast, lacrimal gland, trachea, and nasal cavity.

Clinically, CXPA presents as a firm, asymptomatic mass that can go undetected for years since they are not generally invasive. When the patient does experience any symptoms, with pain being the most common, it is usually due to the mass extending to adjacent structures. If the mass was to involve the facial nerve, paresis or palsy can occur. Other signs and symptoms include skin ulceration, mass enlargement, skin fixation, lymphadenopathy, dental pain, and dysphagia. The onset of symptoms can range anywhere from 1 month up to 60 years (such as with this case), with a mean onset of 9 years. Half of patients will have a painless mass for less than 1 year. Since these symptoms are similar to those of a benign PA, it’s important that the treating physician be aware of the possibility of a CXPA, especially considering the rarity of the cancer.

Grossly, CXPA appears as a firm, ill-defined tumor, and can vary greatly depending on the predominant component. If the PA is the predominant component, the mass may appear gray-blue and translucent, and it could be possible to grossly differentiate between the PA areas and the CXPA areas. If the malignant component predominates, then the mass may contain cystic, hemorrhagic and necrotic areas.

Microscopically, CXPA is defined as having a mixture of a benign PA, admixed with carcinomatous components. Zbaren et al, in an analysis of 19 CXPA cases, found 21% of the tumors were composed of less than 33% carcinoma, 37% of the tumors were composed of 33-66% carcinoma, and 42% of the tumors were composed of greater than 66% carcinoma. Most often, the malignant component is adenocarcinoma, but can also include adenoid cystic carcinoma, mucoepidermoid carcinoma, salivary duct carcinoma, and other less common variations. In cases where the entire tumor is replaced by carcinoma, the diagnosis of CXPA will be based on the presence of a PA on the previous biopsy. Conversely, you could also have a tumor that is predominately composed of a PA, with sparse areas of malignant transformation, such as nuclear pleomorphism, atypical mitotic figures, hemorrhage and necrosis. The likelihood of malignant transformation increases with the length of the PA being present, from 1.5% at 5 years, up to 10% after 15 years.

CXPA can be further sub-divided into four categories based on the extent of invasion of the carcinomatous component outside the capsule: in-situ, non-invasive, minimally invasive, and invasive carcinoma.

#1) In-situ carcinoma occurs when nuclear pleomorphism and atypical mitotic figures are found within the epithelial cells, but do not extend out beyond the border of the myoepithelial cells (Figure 5).

#2) Non-invasive CXPA, which can include in-situ carcinoma, is maintained within the fibrous capsule of the PA, but extends beyond the confines of the myoepithelial cells. Non-invasive CXPA may begin to show malignant transformation, but will overall behave like a benign PA.

#3) Minimally invasive CXPA is defined as <1.5 mm extension into the extracapsular tissue, with a mix of benign PA components and carcinomatous components.

#4) Invasive CXPA is defined as a > 1.5 mm extension into the extracapsular tissue, and will begin to demonstrate more carcinomatous components, such as hemorrhage and necrosis.

As the carcinomatous areas begin to increase in prevalence, the PA nodules will begin to be composed of hyalinized tissue with sparse, scattered ductal structures, and the malignant cells will begin to decrease in size as they move away from the site of origin. Perineural and vascular invasion can be easily identified as the tumor extends into the neighboring tissue (Figure 6).

The development of CXPA has been shown to follow a multi-step model of carcinogenesis with a loss of heterozygosity at chromosomal arms 8q, followed by 12q, and finally 17p. Both PA and CXPA demonstrate the same loss of heterozygosity, however, the carcinomatous components exhibit a slightly higher loss of heterozygosity at 8q, and a significantly higher loss of heterozygosity at 12q and 17q. The early alterations of the chromosomal arm 8q in a PA often involves PLAG1 and MYC, with the malignant transformation of the PA to a CXPA being associated with the 12q genes HMGA2 and MDM2.

Treatment for CXPA involves surgery, radiotherapy and chemotherapy, with a parotidectomy being the most common procedure performed. If a benign PA had originally been resected, but residual remnants of the PA were left behind, then satellite PA nodules will arise in its place (Figure 3). If in-situ, non-invasive or minimally invasive carcinoma is suspected in the superficial lobe of the parotid gland, than a superficial parotidectomy can be performed. Invasive carcinoma will result in a total parotidectomy, with every attempt made to try and preserve the facial nerve. If metastasis is suspected to the cervical lymph nodes, a neck dissection may also be performed. Reconstructive surgery following the removal of the tumor may be necessary, depending on where the tumor was resected from. Other treatment options currently being considered include a combination therapy of trastuzumab and capecitabine, as well as the possibility of a WT1 peptide based immunotherapy.

Figure 5. 40x microphotograph demonstrating an in-situ carcinoma confined within the myoepithelial cells
Figure 6. 10x photomicrograph of carcinoma at the lateral margin with areas of perineural invasion

References

  1. Antony J, Gopalan V, Smith RA, Lam AK. Carcinoma ex pleomorphic adenoma: a comprehensive review of clinical, pathological and molecular data. Head Neck Pathol. 2011;6(1):1–9. doi:10.1007/s12105-011-0281-z
  2. Chooback N, Shen Y, Jones M, et al. Carcinoma ex pleomorphic adenoma: case report and options for systemic therapy. Curr Oncol. 2017;24(3):e251–e254. doi:10.3747/co.24.3588
  3. Di Palma S. Carcinoma ex pleomorphic adenoma, with particular emphasis on early lesions. Head Neck Pathol. 2013;7 Suppl 1(Suppl 1):S68–S76. doi:10.1007/s12105-013-0454-z
  4. Handra-Luca A. Malignant mixed tumor. Pathology Outlines. http://www.pathologyoutlines.com/topic/salivaryglandsmalignantmixedtumor.html. Revised March 21, 2019. Accessed April 5, 2019.

-Cory Nash is a board certified Pathologists’ Assistant, specializing in surgical and gross pathology. He currently works as a Pathologists’ Assistant at the University of Chicago Medical Center. His job involves the macroscopic examination, dissection and tissue submission of surgical specimens, ranging from biopsies to multi-organ resections. Cory has a special interest in head and neck pathology, as well as bone and soft tissue pathology. Cory can be followed on twitter at @iplaywithorgans.

Surgical Pathology Case Study: A 42 Year Old Woman with an Enlarging Mass of the Forearm

Case History

A 42 year old female with a history of neurofibromatosis, hypertension and Hashimoto’s thyroiditis had noted a mass on her forearm approximately 15 years ago. According to the patient, the mass did not change in size and did not cause her any discomfort during that time. Approximately 6 months prior to presenting to her primary physician, the mass began to increase in size and caused discomfort and pain. Upon examination with the Orthopedic Surgery department, a 20 x 20 cm firm, smooth mass on her forearm with mild pain on palpation was noted (Image 1). On MRI, the mass appeared to partially surround the radius and ulna, and encased the median, radial and ulnar nerves. A needle core biopsy was subsequently performed on the mass revealing a high grade malignant peripheral nerve sheath tumor (MPNST). A CT scan of the chest showed no evidence of metastatic disease. During her clinical visit, the use of neoadjuvant chemotherapy and chemoradiotherapy were discussed, but based on the large size of the mass, tumor response would have to be significant in order to allow for limb conserving surgery. At the time that the patient was seen, MPNSTs were not known to be chemosensitive and the chances of significant tumor response was very low (clinical drug trials have since shown some improvements in this area). In light of the poor response to systemic therapy of these tumors and the potentially toxic side effects of chemotherapy, the decision was made to proceed with amputation of the arm through the humerus.

Diagnosis

Frozen sections were sent from all the major peripheral nerves, including the ulnar, radial and median nerves. There was no evidence of any tumor consistent with a high-grade MPNST, although there was evidence of neurofibromas. There were atypical cells with hyperchromasia in the ulnar nerve margin, however, this was not considered to be consistent with a high grade MPNST. Received in the surgical pathology lab was an above elbow amputation consisting of a 30.0 cm long distal arm, an attached hand measuring 17.0 cm in maximum length., and a 4.5 cm long exposed humerus. The specimen is covered by grossly unremarkable skin, with a palpable mass in the mid-portion of the forearm. Sectioning reveals an 18.0 x 12.0 x 11.0 cm well-circumscribed mass composed of bulging, myxoid, white-tan tissue with central areas of hemorrhagic degeneration and yellow-tan friable tissue (Image 2). The bulging white-tan tissue is mainly found peripherally and encompasses approximately two-thirds of the mass. The mass is confined to a thin translucent lining and does not grossly invade neighboring soft tissue or overlying skin. The radial, median and ulnar nerves are adjacent to but not invaded by the mass, although the distal aspect of the mass shares a translucent, myxoid-like tissue with the peripheral nerve sheath of the ulnar and median nerves.

In addition to the standard bone and soft tissue margins that are taken, representative sections of the mass with the closest approach to the overlying skin are submitted. Sections demonstrating the relationship of the distal mass to the radial, median and ulnar nerves are submitted in separate cassettes. Lastly, representative sections sampled from various areas of the mass are submitted in an additional 15 blocks.

Histologically, the tumor consisted of spindle cells arranged in a fascicular pattern with intermittent whorled areas. The cells contained pleomorphic, hyperchromatic nuclei and intervening myxoid hypocellular areas. Mitotic figures were observed with sparse areas of necrosis and hemorrhage. S-100 was ordered on the prior biopsy of the mass, which was weakly positive. Based on these findings, the specimen was signed out as a malignant peripheral nerve sheath tumor.

Image 1. Above elbow amputation with a large forearm mass.
Image 2. Longitudinal cross section of arm demonstrating a bulging, white-tan mass with areas of hemorrhage and necrosis.

Discussion

Malignant peripheral nerve sheath tumors (MPNST) are locally invasive tumors that are associated with medium to large nerves (as opposed to cranial or distal small verves) and commonly recur with eventual metastatic spread. Common sites for metastatic spread include lung, liver, brain, bones and adrenals. They are usually found in adults between the second and fifth decades of life, and account for only 5% of malignant soft tissue tumors. Approximately half of MPNSTs will occur sporadically, with the other half generally arising in the setting of neurofibromatosis type 1 (such as in this case). There is a high clinical suspicion for MPNST if the patient has a history of neurofibromatosis type 1 or if the tumor arises within a major nerve component.

Grossly, MPNST will present as a large, poorly defined, fleshy tumor that runs along a nerve and involves adjacent soft tissue. Often, these tumors will have areas of hemorrhage or necrosis and can track along the length of a nerve. Histologically, the tumors are composed of monomorphic spindle cells arranged in fascicles, palisades and whorls, with compact comma-shaped, wavy or buckled hyperchromatic nuclei with alternating hypocellular foci. (Image 3 and 4). Mitotic figures and necrosis are common, and although S-100 is considered the best marker for MPNST, there is a lack of specificity and sensitivity for immunohistochemical markers. Due to the lack of immunohistochemical markers and molecular findings, as well as the variability associated with the cells, it has traditionally been difficult to diagnose MPNST. The differential diagnosis includes fibrosarcoma, monophasic synovial sarcoma, desmoplastic melanoma, and pleomorphic liposarcoma. Goldblum et al put forth the idea that a diagnosis of MPNST can be made if the tumor falls into any one of the following three categories:

  1. The tumor arises along a peripheral nerve
  2. The tumor arises from a pre-existing benign nerve sheath tumor, such as a neurofibroma
  3. The histologic features are consistent with a malignant Schwann cell tumor

Unfortunately, due to the aggressiveness of the tumor and high recurrence rate, MPNST has a poor prognosis with a 2 year overall survival rate of around 57% and a 5 year survival rate around 39%.

Image 3. Low power photomicrograph showing a spindle cell neoplasm arranged in a fascicular pattern.
Image 4. High power photomicrograph demonstrating spindle cells with hypercellular nuclei in a whorled arrangement and adjacent myxoid hypocellular areas.

References

  1. Case of the week #443. Pathology Outlines. http://www.pathologyoutlines.com/caseofweek/case443.htm. Published November 15, 2017. Accessed March 10, 2019.
  2. Frosch MP, Anthony DC, De Girolami U. Malignant Peripheral Nerve Sheath Tumor. In: Kumar V, Abbas AK, Fausto N, Aster JC. Robbins and Cotran Pathologic Basis of Disease, 8th edition. Philadelphia, PA: Elsevier, Inc. 2010: 1341-1342
  3. Guo A, Liu A, Wei L, Song X. Malignant Peripheral Nerve Sheath Tumors: Differentiation Patterns and Immunohistochemical Features – A Mini-Review and Our New Findings. J Cancer. 2012; 3:303-309. http://www.jcancer.org/v03p0303.html. Accessed March 9, 2019.
  4. Hirbe AC, Cosper PF, Dahiya S, Van Tine BA. Neoadjuvant Ifosfamide and Epirubicin in the Treatment of Malignant Peripheral Nerve Sheath Tumors. Sarcoma. https://www.hindawi.com/journals/sarcoma/2017/3761292/cta/. Accessed March 10, 2019.
  5. Ramnani, DM. Malignant Peripheral Nerve Sheath Tumor. WebPathology. https://www.webpathology.com/case.asp?case=499. Accessed March 9, 2019.
  6. Shankar V. Malignant peripheral nerve sheath tumor (MPNST). Pathology Outlines. http://www.pathologyoutlines.com/topic/softtissuempnst.html. Revised September 12, 2018. Accessed March 9, 2019.

-Cory Nash is a board certified Pathologists’ Assistant, specializing in surgical and gross pathology. He currently works as a Pathologists’ Assistant at the University of Chicago Medical Center. His job involves the macroscopic examination, dissection and tissue submission of surgical specimens, ranging from biopsies to multi-organ resections. Cory has a special interest in head and neck pathology, as well as bone and soft tissue pathology. Cory can be followed on twitter at @iplaywithorgans.

Surgical Pathology Case Study: A 64 Year Old Man with History of Loose Stools and Abdominal Pain

Case History

A 64 year old male presented with a one year history of loose stools, lower abdominal crampy/gassy pain that improved with defection, and an unclear history of melena. A colonoscopy revealed a circumferential, villous, carpet-like lesion extending from 15 cm to the anal verge, with biopsies demonstrating fragments of a villous adenoma. A follow-up CT scan was negative for metastatic disease. The decision was then made to proceed with a low anterior resection with hand-sewn colo-anal anastomosis and diverting loop ileostomy.

Diagnosis

Upon opening the rectum, a 13.8 cm long circumferential, carpet-like lesion is identified, extending to the distal margin (Image 1). Sectioning demonstrated a lesion with a maximum thickness of 1.0 cm, which grossly appears to be confined to the mucosa. Due to the prior biopsy history of a villous adenoma, the entire lesion was completely submitted. This required 116 blocks to be submitted, which were then mapped out to show where each block would have been taken from (Image 2). Although there were many foci of intramucosal carcinoma present, clear cut submucosal invasion was not identified, and the specimen was signed out as a villous adenoma (Image 3).

Image 1. Opened rectum demonstrating the 13.8 cm-long carpet-like lesion.
Image 2. Mapping the lesion to show from where each block is taken.
Image 3. Photomicrograph showing the transition from normal mucosa (black arrow) to villous adenomatous tissue (red arrow).

Discussion

Polyps are an abnormal tissue growth that is a common occurrence within the colon, although they can also be found throughout the small intestine, stomach and esophagus. Polyps can be further classified as being neoplastic or non-neoplastic based on the histological pattern of the cells. The most common types of neoplastic polyps found within the GI tract are colonic adenomas, which are benign polyps that serve as precursors to the majority of colorectal cancers. Nearly half of adults in the Western world will develop adenomas by the age of 50, and there is no gender predilection. It is because of this that it is recommended that all adults get a colonoscopy by the age of 50 (even earlier when there is a family history of developing colorectal cancer).

Most polyps are small, measuring 0.5 cm or less, but can grow to be over 10 cm in size (as seen in this case). When a colonoscopy is performed, these polyps can appear as sessile, meaning flat, or pedunculated, meaning on a stalk. Due to the abnormal epithelial growth of the mucosa, the surface of an adenoma can have a velvety appearance, resembling that of a raspberry. Most patients will not demonstrate any symptoms from their polyps, with the exception of occult bleeding and anemia which are associated with larger polyps.

Dysplasia, which literally means “disordered growth”, occurs when the individual cells lose their uniformity and architecture, often resulting in cells with a hyperchromatic nuclei and a high nuclear to cytoplasmic ratio. The presence of dysplasia contained within the epithelium of a polyp is what classifies the polyp as an adenoma (Image 4). Based on their epithelial growth pattern, adenomas can be classified as either tubular adenomas or villous adenomas. Tubular adenomas tend to be smaller polyps, with a smoother surface and rounded glands on histologic examination. Villous adenomas, in contrast, tend to be larger polyps with long, slender villi noted on histology (Image 5). If an adenoma contains a mixture of tubular and villous elements, they are classified as tubulovillous adenomas. When a dysplastic cell is no longer contained within the epithelium, and instead breaches the basement membrane which separates the epithelium from the underlying tissue, it is termed invasive.

Image 4. Photomicrograph of the villous adenoma, demonstrating the dysplasia that is confined to the mucosa and not extending to the deeper tissue.
Image 5. Photomicrograph of the long, slender villi that are commonly seen in villous adenomas.

What makes this case so interesting is that there is a direct correlation between the size of an adenoma, and the risk of developing colorectal cancer. This is not true with most other cancers, however, as size plays no part in determining whether the tumor is cancerous or not. With colon polyps, the larger the polyp, the greater the chance of developing invasive carcinoma (i.e. cancer). This is why screening colonoscopies are so important. Studies have shown that regular colonoscopies, combined with the removal of the polyps found on the exam, reduce the incidence of colorectal cancer. Why this case is so interesting is that you could assume based on the size of this polypoid lesion, you would find some invasive component. However, after reviewing 116 blocks, not a single focus of invasion could be identified.

It should be stated that although there is a correlation between an adenomas size and the risk of developing cancer, the majority of adenomas will not progress to cancer, and in fact, there are no tools currently available that help to determine why one patient’s adenoma will progress to cancer, while another patient’s adenoma will not.

References

  1. Association of Directors of Anatomic and Surgical Pathology, adapted with permission by the American Cancer Society. Understanding Your Pathology Report: Colon Polyps (Sessile or Traditional Serrated Adenomas). cancer.org. https://www.cancer.org/treatment/understanding-your-diagnosis/tests/understanding-your-pathology-report/colon-pathology/colon-polyps-sessile-or-traditional-serrated-adenomas.html. Accessed February 14, 2019.
  2. Colon Polyps. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/colon-polyps/symptoms-causes/syc-20352875. Accessed February 14, 2019.
  3. Turner JR. Polyps. In: Kumar V, Abbas AK, Fausto N, Aster JC. Robbins and Cotran Pathologic Basis of Disease, 8th edition. Philadelphia, PA: Elsevier, Inc; 2010: 815-820

-Cory Nash is a board certified Pathologists’ Assistant, specializing in surgical and gross pathology. He currently works as a Pathologists’ Assistant at the University of Chicago Medical Center. His job involves the macroscopic examination, dissection and tissue submission of surgical specimens, ranging from biopsies to multi-organ resections. Cory has a special interest in head and neck pathology, as well as bone and soft tissue pathology. Cory can be followed on twitter at @iplaywithorgans.