Microbiology Case Study: An 81 Year Old Female with Persistent Fevers

Case History

The infectious disease service was consulted on an 81 year old female for persistent fevers. She initially presented a few weeks prior with cough & shortness of breath which was diagnosed as an acute chronic obstructive pulmonary disease (COPD) exacerbation for which she received levofloxacin and steroids. The patient continued to have a persistent cough and dysphagia after discharge. Her respiratory status and cough worsened and she was readmitted and intubated. Vancomycin, piperacillin/tazobactam and levofloxacin were started as well as fluconazole for suspected esophageal candidiasis. Her past medical history was significant for breast cancer, atrial fibrillation, and diabetes mellitus. Of note, patient was originally from Puerto Rico but moved to the United States 40 years ago and denied recent travel and any known tuberculosis exposures. She formerly worked in a deli packing cheeses. A bronchoscopy was performed and a brochoalveolar lavage (BAL) specimen as well as blood and stool specimens were submitted for bacterial culture and ova and parasite exam.

Laboratory Identification

Image 1. Multiple larval forms in the stood specimen from an ova and parasite exam. (Iodine stain, 100X).
Image 2. High power of the larvae with a short buccal cavity (red arrow) and prominent genital primordium (blue arrow), (Iodine stain, 1000x).

The bronchoscopy revealed a bloody fluid admixed with clots which was clinically consistent with diffuse alveolar hemorrhage. The roundworms depicted above were identified in both the BAL and stool O&P exam. Based on the presence of the short buccal cavity and the prominent genital primordium and the absence of eggs, the identification of Strongyloides stercoralis was made. Given the large amount of larvae present in both the lungs and gastrointestinal tract, the patient was diagnosed with a strongyloidiasis hyperinfection.  

Discussion

Strongyloides stercoralis is classified as a nematode (roundworm) and is the cause of strongyloidiasis in humans. The helminth is found worldwide, especially in warm climates and underdeveloped countries, and is the cause of 30-100 million infections. Infection is due to fecal contamination of soil, where free-living forms are found, or water. Infective filariform larvae penetrate intact skin, particularly bare feet, resulting in infection. The free living cycle begins with the rhabditiform larvae passed through the stool develops into the infective filariform larvae or when the  rhabditiform larvae mature into free living adult male & female forms that mate and produce eggs which then hatch and become infective filariform larvae that can infect humans. The parasitic life cycle begins with the infective filariform larvae penetrates human skin. The worm is then either coughed up from the lungs and swallowed or migrates to the small intestine where eggs are laid and hatch.

Patients may present with gastrointestinal symptoms such as abdominal pain, bloating, and diarrhea, pulmonary symptoms like dry cough and throat irritation, or skin rashes along points of entry (feet, ankles). When the larvae are in the lung, Loeffler’s syndrome, characterized by pneumonia symptoms with coughing and wheezing, may develop due to an accumulation of eosinophils in response to the parasitic infection. In patients who are immunocompromised, the rhabditiform larvae can develop into the filariform larvae in the host and can directly penetrate the bowel mucosa or perianal skin resulting in autoinfection, dissemination throughout the body, and high parasite burden. Symptoms of hyperinfection include bloody diarrhea, bowel perforation, destruction of lung parenchyma with bloody sputum, meningitis, and septicemia. Hyperinfection most commonly occurs after steroid administration for asthma or COPD exacerbation, but can also be seen in those receiving chemotherapy or who have had organ transplants.  

In the laboratory, the diagnosis of S. stercoralis is most often made by an ova and parasite exam of the stool, duodenal fluid, sputum or BAL specimens (Image 1). Most commonly the rhabditiform larvae are present and are identified by the presence of a short buccal cavity and prominent genital primordium (Image 2). These two features are helpful in distinguishing S. stercoralis from hookworms (Ancylostoma spp. and Necator americanus) which have a longer buccal cavity and indistinct genital primordium. The eggs of these two nematodes are also very similar, although typically S. stercoralis eggs hatch before they are passed in stool specimens. S. stercoralis can also be visualized on H&E histology sections in the crypts of intestinal biopsies where the adult female measures up to 2.2 mm in length. Finally, serologic testing can be helpful when there is a high suspicion of disease in the face of multiple negative stool exams, but cannot distinguish between a current or past infection. Most patients do not remember a specific exposure and prevention includes wearing gloves and shoes when handling or walking on soil that may contain contaminated fecal material. Treatment options for an acute or chronic S. stercoralis include a short course of ivermectin or albendazole. In the case of disseminated infection, ivermectin should be given until stool and sputum exams are negative for 2 weeks. In the case of our patient, she was started on ivermectin, but succumbed to the disease due to extensive pulmonary hemorrhage.   

-Jaswinder Kaur, MD, is a fourth year Anatomic and Clinical Pathology resident at the University of Mississippi Medical Center. 

-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. She is the Director of Clinical Pathology as well as the Microbiology and Serology Laboratories. Her interests include infectious disease histology, process and quality improvement, and resident education.

Microbiology Case Study: A 54 Year Old Male with Right Upper Quadrant Pain

Case History

A 54 year old male with a past medical history of Type II diabetes mellitus and obesity was admitted for a few days history of severe pain over right upper quadrant accompanied by fevers, chills, nausea, vomiting and diarrhea. Physical exam revealed a palpable gallbladder. Ultrasound imaging showed a distended gallbladder with a thickened, edematous and hyperemic wall that was interpreted as acalculus cholecystitis. The patient underwent percutaneous drainage of the gallbladder with plans to undergo a cholecystectomy once the acute phase of his illness stopped. The gallbladder fluid was sent to microbiology for analysis.

Laboratory Findings

Anaerobic plates obtained from organisms growing in thioglycollate broth grew low, convex opaque white colonies. The organisms did not produce the classic double zone of beta hemolysis (Image 1).  Gram stain of the culture showed gram positive bacilli that were “boxcar” shaped (Image 2). Aerobic plates had no growth. The organisms were catalase negative and non-motile. MALDI-TOF identified the organism as Clostridium perfringens.

Image 1. Growth on CNA plate in anaerobic environment
Image 2. Gram stain from the anaerobic culture shows boxcar-shaped gram positive bacilli.

The patient was also placed on piperacillin-tazobactam while in the hospital.  His condition improved and he was discharged home with a seven day course of cefpodoxime and metronidazole with a general surgery follow up appointment.

Discussion

Clostridium perfringens is a gram positive bacilli with blunt ends (boxcar shaped). These obligate anaerobes are spore formers, however these are rarely seen. When seen, they produce subterminal spores. These organisms cause of crepitant myonecrosis (gas gangrene), gangrenous cholecystitis, septicemia, and food poisoning.  They are present in large numbers as normal microbiota in the gastro-intestinal tract of humans and animals, the female genital tract and oral mucosa. Typically, infections are caused by endogenous strains gaining access to normal sterile sites due to a predisposing factor that compromise normal anatomy: surgery, trauma, or altered host defense mechanisms (diabetes, burns, immunosuppression, and aspiration).

Penicillin is recommended in most infections, however resistance has been reported. Optimal management of intra-abdominal infection is to achieve appropriate source control and drainage is important.   

References

  1. Tille P. Bailey & Scott’s Diagnostic Microbiology. Fourteenth Edition. Elsevier; 2017.
  2. Murray P. Medical Microbiology. Seventh Edition. Elsevier; 2013.

-Angela Theiss, MD is a 3rd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

Microbiology Case Study: A 19 Year Old Woman Passes a Worm in Her Stool

Case History

A 19 year old woman with no significant past medical history presented to an outside clinic with psychological distress after passing a worm per rectum. She had no other complaints or symptoms.

Image 1. Eggs are spherical, 31 to 43 μm in diameter, with a thick yellow-brown (bile-stained) shell having radial striations and contain a hexacanth oncosphere (Image courtesy of: Fred Patterson, Parasitologist).
Image 2. Adult proglottids are longer (up to 20 mm) than they are wide (up to 7 mm) and have a genital pore (*) at the lateral margin.
Image 3. Formalin-fixed paraffin-embedded H&E stained section of a proglottid’s lateral uterine branches on each side of a central uterine stem (20x).

Discussion

Adult cestodes (tapeworms) have long, ribbon-like bodies made up of proglottids (egg-producing segments) that develop at the posterior of a scolex (specialized structure for attachment to the small intestine of a host). Taenia has 32 species, 2 of which are medically important for causing taeniasis: Taenia saginata and Taenia solium (beef and pork tapeworm infection, respectively). These parasites are distributed worldwide, with T. saginata being more common than T. solium.

The lifecycle of Taenia involves adult, egg, and larval stages. Adults release gravid proglottids and eggs that are passed in feces. The eggs reach pasture land via soil or water and are ingested by an intermediate host. For T. saginata, the intermediate host is a herbivore (cow), as eggs of T. saginata do not infect humans, and for T. solium, the intermediate host is a pig, human, or other animal. Ingested eggs hatch and release the hexacanth oncosphere (6-hooked embryo) that can penetrate tissues. Over 2 to 3 months, infective cysticerci (0.5 to 2.0 mm in diameter larvae) develop in muscles. Of note, only T. solium can cause cysticercosis (extra-intestinal larval forms within human tissues, ie. the human becomes the intermediate host) and this can be life-threatening if cysticerci invade the brain. When humans consume raw or undercooked beef/pork meat that is infected, cysticerci will attach to the small intestinal mucosa and, over 3 to 5 months, mature into the adult form. The adult T. saginata can reach 4 to 12 meters in length and the adult T. solium can reach 1.5 to 8 meters in length. Adult tapeworms can live within intestines for over 25 years while gravid proglottids and eggs are passed in stool.

Infections are usually asymptomatic or cause mild indigestion, anorexia, and abdominal discomfort. The eggs can be identified by ova and parasite examination (Figure 1) or a cellulose tape preparation of perianal skin. The oncosphere must be visualized to avoid misidentifying a pollen grain. However, eggs of Taenia species and Echinococcus species are indistinguishable. Diagnosis is also made by recovering gravid proglottids from the anal opening or passed in feces (Figures 2 and 3). Distinguishing the two species can be done by examining gravid proglottids for the number of lateral uterine branches present on one side of a central uterine stem. T. saginata have 15 to 30 lateral uterine branches while T. solium have 7 to 13 branches. Both species have a small anterior scolex (measuring 1 to 2 mm in diameter for T. saginata and 1 mm in diameter for T. solium) with 4 suckers. Definitive identification is possible since T. solium’s scolex has a rostellum (crown) with 2 rows of hooks whereas T. saginata’s scolex bears no rostellum or hooks. Treatment is a single dose of praziquantel and successful treatment is defined as passing zero proglottids over 4 consecutive months.

-Adina Bodolan, MD is a 3rd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

Microbiology Case Study: A 65 Year Old Female with Altered Mental Status

Case History

A 65 year old female with a past medical history significant for hypertension, type 2 diabetes, and asplenia, presented to a regional hospital with shortness of breath and altered mental status after the patient’s spouse found them obtunded. Emergency room workup was significant for hypoxia, acidosis, leukocytosis, and acute kidney injury with CT chest imaging showing multifocal right lung infiltrates concerning for aspiration pneumonia. The patient was started on broad spectrum antibiotics but subsequently developed increasing respiratory distress requiring intubation. The patient was transferred to our institution for further management.

Laboratory Findings

Additional testing revealed negative RSV, influenza PCR, and S. pneumoniae and Legionella urinary antigen tests. A sputum culture grew E. coli susceptible to several antibiotics and the antibiotic therapy was narrowed to doxycycline. The patient improved clinically and was transferred back to the regional hospital. Two days after transfer, one blood culture bottle which was collected upon admission to our institution (about 5 days prior), flagged positive for microbial growth. Gram stain revealed budding yeast forms, which were subsequent identified as Candida glabrata.

Image 1. Gram stain from blood culture showing budding yeast forms.
Image 2. Wet mount from a growth plate showing yeast without pseudohyphae
Image 3. Potato flake agar showing smooth creamy white colonies.

Discussion

Candida glabrata is a yeast which can cause infections of the bloodstream as well as urogenital tract and infections of the mucosal surfaces such as the oral cavity. Patients at increased risk for infection include immunocompromised patients, especially patients on immunosuppressant drugs, chemotherapeutic agents which cause neutropenia, and antibiotics. There has been an increasing incidence of systemic and mucosal yeast infection, thought to be due to the increasing use of immunosuppressing therapies as well as broad spectrum antibiotics. Candida species have been reported in some centers as the fourth most common cause of bloodstream infections and after Candida albicans, Candida glabrata has been reported as the second most frequent Candida species to cause nosocomial yeast infections. Candida glabrata is a significant pathogen as it can be resistant to azole antifungals, amphotericin, and echinocandins. There are several mechanisms of resistance to azoles which Candida glabrata utilizes including upregulation of genes CgCDR1 and CgCDR2 which encode drug efflux pumps. In addition, Candida glabrata also can have mutations in gene CgERG11, the usual enzymatic target of the azole antifungal drugs.

Candida glabrata appears as a budding yeast on gram stain with smooth white to cream colonies on agar plates. Microscopically, Candida glabrata appears as an oval yeast with single terminal budding. Distinguishing morphologic features of Candida glabrata include not forming pseudohypae at 37 degrees and not producing germ tubes in in vitro assays. Candida glabrata will also utilize the carbohydrate trehalose.

In some clinical cases, it is difficult to determine whether a Candida species recovered from culture represent an actual pathogen or a normal colonizer which was carried into the culture during collection. Candida species are normal commensal organisms of mucosal surfaces as well as skin, making it important to correlate clinical findings which microbial culture results. In this case, the patient had been stabilized and demonstrated great clinical improvement a few days prior to the positive blood culture result. Thus, this positive blood culture for Candida glabrata most likely represents a case where normal skin flora was inadvertently cultured.

-Liam Donnelly, MD is a 1st year anatomic and clinical pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

Microbiology Case Study: A 58 Year Old Female with Shortness of Breath, Fever, and Chills

Case History

A 58 year old female presented to the emergency department with a chief complaint of shortness of breath, fevers and chills since the previous day. Her past medical history is significant for chronic obstructive pulmonary disease, hypertension, and borderline personality disorder. Vitals signs were significant for an oxygen saturation of 88%. Physical examination of the patient was difficult as the patient became increasingly agitated, however, the patient appeared in no acute distress with moist mucous membranes, anterior lung fields were clear to auscultation, there were no cardiac murmurs, and examination of their skin revealed no rashes or lesions.

Laboratory Findings

Laboratory tests were significant for a lactate level of 2.5 with a white blood cell count and complete metabolic panel within normal limits. Chest x-ray did not show evidence of consolidation or interstitial infiltrates. Urinalysis was within normal limits. One set of blood cultures was also drawn during this initial encounter. The patient became increasingly agitated after initial examination and was discharged with some laboratory tests pending. After incubating for 20 hours, the aerobic blood culture bottle flagged positive for bacterial growth, with gram stain demonstrating a gram negative coccobacillus and a rapid Verigene identification of Acinetobacter. The patient came back to the emergency department the next day with stable vital signs and unremarkable complete blood count and chest x-ray. The patient was started on meropenem which was switched to ciprofloxacin two days later, after bacterial antibiotic susceptibility results showed susceptibility to carbapenems, amikacin, amp/sulbactam, ceftazidime, ciprofloxacin, gentamin and tobramycin.

Image 1. Gram negative coccobacilli characteristic of Acinetobacter on Gram stain.
Image 2. Acinetobacter morphology on MacConkey agar.

Discussion

Acinetobacter is a genus of gram negative bacteria, with some genospecies identified as human pathogens including species in the A. calcoaceticus-A. baumannii complex (ACB) which are difficult to differentiate by phenotypic characteristics. Species in the ACB include genospecies 1 (A. calcoaceticus), genospecies 2 (A. baumannii), genospecies 3, and genospecies 13TU.

In the laboratory, Acinetobacter appear as non-pigmented mucoid, domed colonies with a smooth surface on growth media. Acinetobacter are non-motile, aerobic, catalase positive, oxidase negative, indole negative bacteria. Acinetobacter are also non-glucose fermenters and do not utilize lactose.

Out of the ACB genospecies, A. baumannii is considered the most significant pathogen, causing 80% of nosocomial infection. A. baumannii is an environmental bacteria which inhabits soil and water. In hospital settings, A. baumannii can survive on environmental surfaces for extended periods of time and is resistant to desiccation and cleaning solutions. The most common settings in which A. baumannii infections occur are within intensive care units where there are immunocompromised patients utilizing medical devices such as ventilators or catheters which are surfaces A. baumannii frequently colonizes. Not surprisingly, sites where these medical devices preside are the most common sites of infection for A. baumannii including the respiratory tract (hospital acquired pneumonia), bloodstream infections, and wound infections. Interestingly, A. baumannii wound infection have also been seen at a high prevalence in wartime and disaster victims. A. baumannii has been recovered in 63% of wounds from soldiers in Iraq and Afghanistan and 20% of wounds from victims after a tsunami in 2004.

 Importantly, A. baumannii can be resistant to several classes of antibiotics including fluroquinolones (DNA topoisomerase mutations), aminoglycosides (transposons), beta lactams (AMP C beta lactamase), and carbapenems (OXA carbapenemase), making infections with multidrug resistant organisms challenging to treat. In this case, the microbe had an OXA carbapenemase but was susceptible to carbapenems. In addition, this patient’s relatively benign presentation and normal laboratory results raise the question of whether this bacteria was causing a bloodstream infection or was simply a skin colonizer which grew after being inoculated into the blood culture media. Acinetobacter, in addition to colonizing hospital equipment and surfaces is a common colonizer of the skin as well as respiratory tract of patients on respiratory ventilators. Thus, Acinetobacter can be inadvertently cultured in blood and sputum samples, making correlation of the patient’s clinical symptoms and signs with culture results very important.   

-Liam Donnelly, MD is a 1st year anatomic and clinical pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

Microbiology Case Study: A Male in his Early 20s with Generalized Body Aches

Clinical History

An African American male in his early 20s presented to the emergency department (ED) with complaints of a sore throat, headache, generalized body aches, and fatigue for the past week. He also noted intermittent fever and chills as well as some nausea with a decrease in his appetite. He had been seen multiple times in the ED recently for similar symptoms. His past medical history was non-contributory and he noted no significant travel or exposure history with the exception of attending a local party 10 days ago. His temperature was 100.5°F and vitals were otherwise normal. His physical exam was normal with the exception of dry mucous membranes indicating mild dehydration. Initial laboratory testing showed a leukopenia (white blood cell count of 1.5 TH/cm2) with 39% lymphocytes and rapid antigen testing for group A Streptococcus, influenza, and infectious mononucleosis were negative. The patient was admitted for further work up due to the prolonged nature of his symptoms.   

Laboratory Identification

Results from additional infectious disease testing are in the table below.

This pattern of results is most consistent an acute HIV infection.

Discussion

Human immunodeficiency virus (HIV) is an enveloped, single stranded RNA virus which belongs to the family Retroviridae. HIV is most commonly sexually transmitted via body fluids such as blood, semen, and vaginal secretions directly contacting mucosa membranes. HIV can also be transmitted due to needle stick injuries, blood transfusions, and transplacentally from infected mother to fetus or by breast feeding. Acute HIV illness presents as a mononucleosis-like syndrome with fever, pharyngitis, arthralgias, malaise, and weight loss. During this acute illness, the HIV RNA viral load is extremely high. After a period of clinical latency, which on average is approximately 10 years, there is a deterioration of the immune system, the CD4 count drops, and the patient is at risk for opportunistic infections and neoplastic diseases.

Based on the 2014 CDC/APHL guidelines, the initial screening test for HIV is an antigen-antibody combination assay. These immunoassay based tests detect the p24 antigen and antibodies to HIV-1 and HIV-2 (see image below). By testing for the p24 antigen in addition to HIV antibodies the time to a positive patient result is decreased (window period) as p24 is one of the first viral proteins to appear, even before antibodies are present.    

If the antigen-antibody test is repeatedly positive, the second step in the testing algorithm is an antibody differentiation assay. This test has taken the place of the Western blot and Western blot is no longer recommended in the diagnosis of HIV. If the antibody differentiation test is positive, the diagnosis of HIV-1 or HIV-2 is confirmed. As this step only detects the presence of antibodies, the differentiation test will be negative in an acute HIV infection.

If there is a discrepancy between the first two steps in the testing algorithm or an indeterminate result is obtained, the final step involves nucleic acid amplification testing (NAAT) to detect viral RNA. Viral RNA is the first HIV-1 specific marker to appear following infection. In the case of an acute or untreated long term infection, the viral load can approach levels up to 100 million copies.  

When additional history was obtained from our patient, he said he was sexually active with a new male partner in the past few weeks and did not use protection. He stated he had been treated with Chlamydia in the past. Further testing for CD4 count, other opportunist & sexually transmitted infections, and HIV genotype testing was performed and outpatient HIV care was arranged for the patient. 

-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. She is the Director of Clinical Pathology as well as the Microbiology and Serology Laboratories. Her interests include infectious disease histology, process and quality improvement, and resident education.

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.