What’s in a Differential?

When a complete blood count (CBC) and differential is ordered by a physician, most labs today have instrumentation capable of performing an automated differential. Depending on the instrument results and flags, we may need to perform a scan, review of the slide, or a manual differential. However, the definition of a manual differential today may be a bit different than the historical definition. A typical manual differential, when I first started working as a technologist, consisted of counting and differentiating 100 white blood cells under a microscope, and performing a red blood cell morphology along with a platelet estimate. Today, the 3 components of the manual differential have not changed, but more and more  labs are using an automated digital counting device, such as CellaVision. Whether counting cells under the microscope or scanning and verifying or reclassifying cells in CellaVision, it is important to always address all 3 parts of the manual review.

When an automated CBC has flagged that abnormal RBC morphology may be present, a peripheral blood smear should be reviewed. Reporting the red blood cell (RBC) morphology is an important component of a differential. Evaluation and interpretation of RBC morphology may provide the physician with important diagnostic information regarding the underlying cause of a variety of disorders, including anemia and systemic disease. Therefore, it is important to be able to accurately recognize and identify RBC morphologic abnormalities.

Red blood cell morphology can be subjective, and therefore inconsistent. Therefore, Laboratories must have training and competency programs as well as  procedures which dictate how they will report RBC morphology. Some labs use a numbering system, 1+, 2+, 3+, and others report, ‘rare’, ‘few’, moderate’ or ‘many’. Some morphological, such as rouleaux, can just be reported as present, with no quantified. Any method is acceptable, as long as there is consistency in reporting.

When performing RBC morphology,  these semi-quantitative report formats for should be based on clinical significance. Some RBC morphologies and inclusions are clinically significant,even when they are present in very low numbers. Sickle cells are one of these abnormalities that are significant even if only seen in very small numbers. Malaria or other parasites are clinically significant in any number. Fragmented cells such as schistocytes and helmet cells should also be noted if seen in any number. Other abnormalities which can be clinically significant in very low numbers are polychromasia, spherocytes and teardrop cells.

There are many other abnormal RBC morphologies which are only clinically significant if seen in larger numbers. Laboratories may choose to only report the presence of ovalocytes, target cells, burr cells, macrocytes, microcytes or hypochromia when greater than a defined percentage of cells exhibit these morphologies. Other laboratories choose to not report macrocytes, microcytes and hypochromia at all, instead relying on the physician to use the RBC indicies for their indication. The 2 most important things to remember, whatever your procedures are, is to be consistent, and not to ignore the:RBC morphology.

In addition to performing RBC morphology, a manual differential also requires platelet examination. A smear should be examined for a platelet estimate and abnormalities. This is particularly important when platelet clumps or an abnormal platelet scattergram are flagged on the CBC.  If an instrument uses optical platelet counts, large platelets can be missed. A fluorescent platelet count (PLT-F) , performed on Sysmex analyzers, will stain only platelets and give an accurate platelet count. The fluorescent count eliminates interferences seen with other methods. However, even when reporting a PLT-F, it may still required to review the smear for a platelet estimate, particularly with a very low count, or with clumped platelet flags. Clumped platelets are not an uncommon phenomenon, and an accurate platelet count can not be reported if significant clumping is present. The presence of giant platelets or hypogranular platelets, seen on the slide,  can also aid the physician in diagnosis or patient management.

CellaVision users have the added benefit of automation which simplifies the process of performing manual differentials. The system automatically locates and takes digital images of cells, including white blood cells, red blood cells and platelets.This simplifies the process of performing a manual differential. White  blood cells are pre-classified, RBC images are provided, and platelet images allow platelet estimates to be performed easily. The new advanced RBC application software can pre-classify RBCs.  This makes it even easier than before to perform reliable, standardized RBC morphology. (Watch for my next Hematology blog about the new RBC software!)

Particular disorders or abnormalities often involve characteristic changes to RBC morphology “Assessment of RBC morphology can be the best tool for laboratory hematology professionals to recommend clinical and laboratory follow‐up in a patient with anemia and to select the right tests for definitive diagnosis.”1 Too often, I have seen technologists perform a manual differential and either superficially skim over the RBC and platelet components, or totally forget them. Don’t forget your RBC morphology and platelet estimate and morphology! With today’s automated differential and autovalidation, 75-85% of CBCs are autovalidated. This allows us to spend quality time on those manual reviews that need to be done. Be sure to spend your time thoroughly reviewing the slides. A scan, slide review or manual differential, whether done under the scope of with CellaVision,tells the physician that we have looked at the slide or cells, which must include all 3 parts of manual review… WBCs , RBCs and platelets. Don’t sign it out until it’s complete!


  1. J. Ford, Red Blood Cell Morphology. International Journal of Laboratory Hematology. 2013
  2. https://www.labce.com/red-cell-morphology.aspx

-Becky Socha, MS, MLS(ASCP)CM BB CM graduated from Merrimack College in N. Andover, Massachusetts with a BS in Medical Technology and completed her MS in Clinical Laboratory Sciences at the University of Massachusetts, Lowell. She has worked as a Medical Technologist for over 30 years. She’s worked in all areas of the clinical laboratory, but has a special interest in Hematology and Blood Banking. When she’s not busy being a mad scientist, she can be found outside riding her bicycle.

Hormone Blockers = Blood Letting for Female Athlete with high T?

Caster Semenya celebrates as she wins gold in the women’s 800 meters in the Commonwealth Games on April 13, 2018, on Australia’s Gold Coast (1). Jason O’Brien/Getty Images

I will continue this month along the thread of last month’s post, which addressed the controversy surrounding South African female mid-distance runner Caster Semenya. Caster has won many international mid-distance races (400-800m), but she has been suspected of naturally producing higher levels of testosterone.

Since last month, I’ve learned the reason for the higher testosterone is uncertain: it could be due to natural production (hyperandrogenism) or rumors of her being intersex1. Regardless, what I will discuss here is how the proposed actions of the International Olympic Committee would be expected to affect Semenya’s performance. Specifically, how would lowering testosterone levels affect her athletic performance?

Last month, we saw that muscle mass might be expected to decrease, but this may not affect athletic performance significantly.

Another important effect of testosterone is on red blood cell levels including hemoglobin, which by carrying oxygen to muscle is a central part of calculating VO2max. VO2max is maximal oxygen consumption. This is strongly linked to performance in cardiovascular athletic events.

Mid-distance running requires a large cardiovascular capacity. Maybe not the same level of Tour-de-France long distance bikers in the Alps, but still substantial. As a runner that feels pretty proud at having run a sub-3 minute 800m, I can say Caster’s feat of running it in less than 2 minutes is incomprehensible. From the burning feeling in my lungs and thudding, maximum heart rate at the end of the half-mile, I can attest that this event requires substantial cardiovascular efficiency.

Maximal oxygen consumption (VO2max) by exercising skeletal muscle is principally limited most by cardiac output and oxygen-carrying hemoglobin levels. This has been shown quite convincingly in a series of experiments in the 1950’s-70’s2,3 that probably wouldn’t be approved by the IRBs of today charged to protect research subject rights.

First, transfusing blood increased hemoglobin concentration and similarly the VO2max and exercise endurance of participants.  (This practice was exploited most notably later on in the Tour de France).  In other studies3, blood was removed from participants before assessing their exercise tolerance (10% loss of hemoglobin à 13% reduction in VO2max). Another study removed 400mL, 800mL and 1,200mL over several days, which decreased hemoglobin by 10%, 15%, and 18% respectively. There was a concomitant decrease in endurance time (-13%, -21%, -30%) and VO2max as well (-6%, -10%, -16%)3.  A summary of blood transfusion and hemodilution studies is shown in Figure 1 from Otto JM et al4.

Figure 1. Reproduced from Otto JM et al (4)

In transgender women (gender incongruent with sex assigned male at birth), hormone therapy to increase estrogen levels (oral estradiol) and block testosterone (anti-androgen: spironolactone) reduces hemoglobin by 9% on average (from 15.2 g/dL to 13.9 g/dL)5. I would expect a smaller decrease for Semenya as she will likely not get a full dose hormone regimen used for transgender transition and because her testosterone levels wouldn’t be as high as biologic males’.  However, she would still be expected to have lower hemoglobin- similar to donating a half or whole unit of blood. If hemoglobin decreased even just 5%, that could affect her performance substantially when the difference between competitors boils down to seconds in mid-distance races.

Arguably, forced blood donation could produce the same effects as testosterone-lowering therapy. But it would be far too dramatic to suggest something like bloodletting by the International Olympic Committee.

In the end, I don’t feel qualified to say what should be done in this case. All I can say is that I don’t think lowering Caster Semanya’s testosterone levels will have the intended effect of decreasing muscle mass. On the other hand, it would decrease hemoglobin levels tempering her performance. But who should determine the point where her hormone levels should be? There is such a strong biologic connection between hormone levels and physiology that manipulating them for athletic fairness could be akin to playing puppeteer.


  1. North, Anna. ““I am a woman and I am fast”: what Caster Semenya’s story says about gender and race in sports” Vox. May 3, 2019
  2. BALKE B, GRILLO GP, KONECCI EB, LUFT UC. Work capacity after blood donation. J Appl Physiol. 1954 Nov; 7(3):231-8.
  3. Ekblom B, Goldbarg AN, Gullbring B. Response to exercise after blood loss and reinfusion. J Appl Physiol. 1972 Aug; 33(2):175-80.
  4. Otto JM, Montgomery HE, Richards T. Haemoglobin concentration and mass as determinants of exercise performance and of surgical outcome. Extrem Physiol Med. 2013; 2: 33.
  5. SoRelle JA, Jiao R, Gao E et al. Impact of Hormone Therapy on Laboratory Values in Transgender Patients. Clin Chem. 2019; 65(1): 170-179.

-Jeff SoRelle, MD is a Molecular Genetic Pathology fellow at the University of Texas Southwestern Medical Center in Dallas, TX. His clinical research interests include understanding how the lab intersects with transgender healthcare and advancing quality in molecular diagnostics.

Hematopathology Case Study: A 77 Year Old Man with Rash

Case History

The patient is a 77 year old man with a longstanding history of increased white blood cell (WBC) count who presented with a new rash and increasing absolute lymphocytosis.


Peripheral Blood Smear

Peripheral blood smear shows small to medium-sized lymphocytes with basophilic cytoplasm, cytoplasmic protrusions or blebs, round to oval nuclei with indented nuclear contours and some cells with prominent nucleoli.

Bone Marrow Biopsy

Bone marrow aspirate (top left) shows increased lymphocytes with similar features to those seen in the peripheral blood. The core biopsy (top right) shows an abnormal lymphocytic infiltrate. By immunohistochemistry, CD3 highlights markedly increased interstitial T-lymphocytes (30-40%) that predominantly express CD4. CD8 highlights only few scattered T-cells.

Flow Cytometry

Concurrent flow cytometry identifies an expanded population of lymphocytes comprising 73% of the total cellularity. Of the lymphocytes, 98% are T-cells. The T-cell population is almost entirely composed of CD4 positive cells (CD4/8 ratio = 301). The T-cells show expression of TCR (a/b), normal T-cell antigens CD3, CD2, CD5 and CD7 and express CD52 (bright).


Concurrent chromosome analysis shows that 90% of the metaphase bone marrow cells examined have a complex abnormal karyotype with a paracentric inversion of chromosome 14 that results in the TRA/D/TCL1 gene rearrangement. There is also a rearrangement resulting in three copies of 8q with partial loss of 8p as well as other chromosome aberrations.


Altogether, the presence of an abnormal CD4 positive and CD52 (bright) lymphocyte population with the characteristic cytogenetic finding of inv(14), is diagnostic of T-cell prolymphocytic leukemia (T-PLL). This patient’s course is unusual in that he initially presented with indolent disease that ultimately progressed. The lymphocyte morphology was also somewhat atypical in that only occasional cells had prominent nucleoli. This is consistent with the “small cell variant” of T-PLL.


T-PLL is generally an aggressive disorder characterized by small to medium sized mature T-cells that are found in the peripheral blood, bone marrow, lymph nodes, spleen, liver and sometimes skin. T-PLL is rare and occurs in adults usually over 30 years old. The clinical presentation includes a lymphocytosis, often >100 x 10^9/L, hepatosplenomegaly and lymphadenopathy. Serous effusions and skin infiltration can be seen in a subset of cases. On microscopy, the cells are usually small to medium in size with basophilic cytoplasm, round to irregular nuclei and visible nucleoli. Characteristic cytoplasmic blebs or protrusions are a common feature. The immunophenotype is of a mature T-cell and cells are positive for CD2, CD3, CD5 and CD7. They are negative for TdT and CD1a. Another characteristic feature is bright expression of CD52. Sixty percent of cases are positive for CD4, while 25% show double expression of CD4 and CD8. The most frequent chromosome abnormality is inversion of chromosome 14 at q11 and q32, which is seen in 80% of patients. Translocations involving chromosome X and 14 are also seen, as well as abnormalities of chromosome 8. The overall prognosis is generally poor with a median survival of 1-2 years. Patients with expression of CD52 may respond well to the monoclonal anti-CD52 antibody alemtuzumab, but other treatment options are limited.1

The small cell variant (SV) of T-cell prolymphocytic leukemia was once referred to as T-cell chronic lymphocytic leukemia due to a predominant population of small lymphocytes with condensed chromatin and lack of conspicuous nucleoli. In addition, unlike the aggressive course seen in most patients with T-PLL, patients with this morphology tended to have an indolent or more chronic disease course. Eventually, it became clear that this was merely a variant of T-PLL due to similar immunophenotypic and cytogenetic findings. Ultimately, the term T-cell CLL was retired from use.2

In a comparison of patients with SV T-PLL to three large studies of classic T-PLL patients, the SV patients were found to have a higher frequency of a normal karyotype and increased double negative (CD4-/CD8) immunophenotype. Interestingly, 38% of the SV patients did not receive treatment for the entire duration of follow-up, while 19% required treatment after initially just being observed. This time period ranged between 2 months to 3 years. The remaining patients were treated at diagnosis. Most of the patients ultimately progressed and the cause of death was disease progression in 86% of the patients who died during follow-up. Overall, SV T-PLL tended to show less aggressive clinical behavior than classic T-PLL, however many aggressive cases of patients with the small cell variant have been seen. Likewise, more indolent cases of classic T-PLL featuring cells with larger nuclei with prominent nucleoli have also been described.2

While cases of SV T-PLL may initially present with more indolent disease, they almost always progress to a similarly aggressive disease course as seen in classic T-PLL. T-PLL is generally resistant to most conventional chemotherapies. As mentioned earlier, cases of T-PLL tend to express bright CD52, which is a glycoprotein present on the surface of mature lymphocytes. CAMPATH-1H is an anti-CD52 monoclonal antibody that may result in complement-mediated lysis and antibody-dependent cellular cytotoxicity. In a study by Dearden et. al., thirty-nine patients with T-PLL received CAMPATH-1H treatments. The overall response rate was 76% with 60% achieving complete remission. These rates are significantly higher than those reported for conventional therapies like CHOP. Unfortunately, almost all of the patients ultimately progressed and all but 2 had relapsed following 1 year of therapy. This indicates that CAMPATH-1H is good for first line therapy, but is not a curative treatment for this aggressive and most often deadly disease. 3


  1. Swerdlow SH, Campo E, Harris NL, et al. WHO Classification of Tumours of Haematopoetic and Lymphoid Tissues (Revised 4th edition). IARC: Lyon 2017.
  2. A. Rashidi and S. Fisher. T-cell chronic lymphocytic leukemia or small-cell variant of T-cell prolymphocytic leukemia: a historical perspective and search for consensus. European Journal of Haematology. 2015(Vol 95).
  3. C. Dearden, E. Matutes and B. Cazin, et. al. High remission rate in T-cell prolymphocytic leukemia with CAMPATH-1H. Blood. 2001(98)1721-1726.

Chelsea Marcus, MD is a Hematopathology Fellow at Beth Israel Deaconess Medical Center in Boston, MA. She has a particular interest in High-grade B-Cell lymphomas and the genetic alterations of these lymphomas.

Hematopathology Case Study: A 71 Year Old Man with a History of Multiple Myeloma

Case History

A 71 year old man with a history of multiple myeloma presented with urinary incontinence and confusion and was found to have hyperkalemia with renal failure. Imaging showed extensive inguinal lymphadenopathy with concern for new lymphoma.

Excisional Lymph Node Biopsy

H&E 40x


Sections show an enlarged lymph node with complete effacement of the normal lymph node architecture by sheets of medium and large plasmablastic cells. The cells have round nuclear contours, large prominent nucleoli and moderate amounts of amphophilic cytoplasm. Frequent apoptotic cells and scattered mitoses are seen.

Immunohistochemical stains show that the neoplastic cells are immunoreactive for CD138, CD38, CD19 (dim) and MUM1. They are negative for CD20, which highlights only small admixed B-cells. The cells are kappa restricted by kappa and lambda immunostain. The Ki-67 proliferation index is greater than 90%.

Taken together, the morphologic and immunophenotypic features are of a high grade plasmablastic neoplasm. The differential diagnosis includes plasmablastic myeloma and a plasmablastic lymphoma. Given the patient’s history of a kappa restricted plasma cell dyscrasia, plasmablastic myeloma is favored.


Multiple myeloma is a neoplasm of clonal plasma cells that accounts for 10% of all hematologic malignancies. It is most commonly seen in adult and elderly patients with a male predominance. Plasma cells are generally characterized by the presence of a “clockface” nuclei and distinct perinuclear Hof or clearing of the cytoplasm containing a large number of Golgi bodies. The morphology of plasma cell tumors can range from small mature plasma cells to anaplastic or plasmablastic morphology. In this case, the cells showed plasmablastic (PB) morphology, which is characterized by a large nucleus, large nucleolus, fine reticular nuclear chromatin pattern, lack of nuclear Hof and less abundant cytoplasm than typical plasma cells.1

The differential diagnosis for cases with this morphology primarily includes PB lymphoma and PB myeloma with extramedullary involvement. PB lymphoma is seen more commonly in HIV positive patients or patients with other causes of immunodeficiency. It typically occurs in adults and has a male predominance. The tumor generally presents outside of nodes and is most frequently seen in the oral cavity/jaw. Patients tend to present with advanced stage and bone marrow involvement. While PB lymphoma is categorized as a distinct subtype of diffuse large B-cell lymphoma, PB myeloma is considered an atypical morphologic variant of multiple myeloma and is treated with therapy geared towards plasma cell neoplasms. 2

Making the distinction between these entities is difficult due to similarities in morphology and immunophenotype. Ultimately, the diagnosis is generally made based on the clinical context. In one series of “plasmablastic” neoplasms by Ahn, et. al., 6 out of 11 cases were called PB lymphoma, 2 out of 11 were called multiple myeloma and 3 were called indeterminate. Among the PB lymphoma patients, 4 were either HIV positive or had a history of immunosuppression. All 6 cases were positive for CD138 and negative for CD20 with EBV in situ hybridization positivity in 3 out of 6 cases. The multiple myeloma cases had evidence of end organ damage without lymphadenopathy. One indeterminate case had peritoneal nodules, lytic lesions and an EBV positive neoplasm in the bone marrow, which precluded a definitive diagnosis. 3

The immunophenotypic pattern seen in this case is typical of these neoplasms and is characterized by the expression of plasma cell antigens (CD138, CD38, MUM1) with either weak or negative expression of B-cell antigens (CD20). A study by Vega et. al. looked at the immunophenotypic profiles in nine cases of PB lymphoma and seven cases of PB myeloma. They found that the profiles were nearly identical.  All cases were positive for MUM1/IRF4, CD138 and CD38 and negative for CD20, consistent with a plasma cell immunophenotype. PAX5 and BCL6 were weakly positive in 2/9 and 1/5 PB lymphomas and were negative in all PB myelomas. A high Ki-67, overexpression of P53 and loss of p16 and p27 were present in both tumors. There was no evidence of HHV8 detected in either neoplasm. The presence of EBV-encoded RNA, was seen in all PB lymphoma cases tested and negative in all plasma cell myeloma cases. This was found to be statistically significant. 4

Unfortunately, both PB lymphoma and PB myeloma are aggressive high grade neoplasms with a poor prognosis. A study conducted by Greipp et. al. assessed the prognostic significance of plasmablastic morphology in a cohort of patients from the Eastern Cooperative Oncology Group Myeloma Trial E9486. They looked at bone marrow aspirates from 453 newly diagnosed multiple myeloma cases in a 5 year period. Of the 453 aspirates, 8.2% were classified as PB morphology.  The overall survival of patients with PB morphology was significantly shorter than patients with non-PB morphology with a median of 1.9 years compared to 3.7 years. There did not appear to be a relationship between PB morphology to other clinical or laboratory features such as age, sex, bone lesions or type of M-protein. 5


  1. M Srija, P Zachariah, V Unni, et. al. Plasmablastic myeloma presenting as rapidly progressive renal failure in a young adult, Indian Journal of Nephrology, Volume 24(1): 2014, Page 41-44.
  2. JJ Castillo, M Bibas, RN Miranda, The biology and treatment of plasmablastic lymphoma, Blood, Volume 125, 2015, Page 2323-2330.
  3. J Ahn, R Okal, J Vos, et. al. Plasmablastic Lymphoma vs Myeloma With Plasmablastic Morphology: An Ongoing Diagnostic Dilemma, American Journal of Clinical Pathology, Volume 144(2): 2015, Page A125.
  4. F Vega, CC Chang, LJ Medeiros, et. al. Plasmablastic lymphomas and plasmablastic plasma cell myelomas have nearly identical immunophenotypic profiles. Modern Pathology, Volume 18: 2005, Page 806-815.
  5. PR Greipp, T Leong, J Bennett, et. al. Plasmablastic Morphology – An Independent Prognostic Factor With Clinical and Laboratory Correlates: Eastern Cooperative Oncology Group (ECOG) Myeloma Trial 39486 Report by the ECOG Myeloma Laboratory Group, Blood, Volume 91: 1998, Page 2501-2507.

Chelsea Marcus, MD is a Hematopathology Fellow at Beth Israel Deaconess Medical Center in Boston, MA. She has a particular interest in High-grade B-Cell lymphomas and the genetic alterations of these lymphomas.

Smudge Cells: Artifacts or Clinically Significant?

In today’s hematology lab, when physicians order a CBC with differential, they typically request a CBC with automated differential. Thus, up to 85% of our CBCs are autovalidated because they are entirely within normal range, with no instrument flags. This leaves the technologist time to spend on those slides that do need a manual review. In reviewing a slide, we evaluate the WBCs, RBCs and platelets, and must pay attention to the counts as well as morphology.

But, what do we do when we have a cell we cannot identify? When we perform a manual differential under the microscope, technologists will joke or tell stories about the legendary “skipocyte”; that cell which, while it does not look malignant or clinically significant, we still can’t decide what it is, so it’s skipped. Perhaps the best way to deal with these cells would be to get consensus from other techs or the Hematology supervisor or to request a pathology review. However, despite the fact that we are taught that there is no such thing as a skipocyte, there are times when a tech will ignore the cell, hoping they don’t see another one. But, what do we do when we see smudge cells? Are they skipocytes? What exactly are they? Do we ignore these? Are they clinically significant? Do we count them as their own category of cells? Or something else?

Firstly, what is a smudge cell? Smudge cells, or basket cells, are remnants of leukocytes. They have no cytoplasm, and sometimes all that can be seen are smashed nuclei. Smudge cells are formed from leukocytes, typically lymphocytes, that are fragile, and are destroyed or smudged in the physical process of making a smear. But, what if the instrument makes the smear? In recent years, more labs are using automated analyzers that prepare and stain blood smears. Even though these have instrument settings based on the physical characteristics of each sample, we still tend to observe these traumatic injuries to leukocytes with automated slide making. Whether we make slides manually or the instrument makes them, these fragile cells appear on the stained slide as ruptured cells called smudge cells.

Image 1. Smudge cells seen on peripheral blood smear.

Smudge cells have also been called Gumprecht shadows, named after German scientists and researcher Ferdinand Adolph Gumprecht, who observed these on slides of patients with chronic lymphocytic leukemia (CLL). Smudge cells in patients with CLL are ruptured B-cells, but they can’t be distinguished morphologically from other disintegrated lymphocytes. We also see leukocytosis and smudge cells in viral conditions and chronic inflammatory diseases. However, the term Gumprecht shadows is reserved only for smudge cells in CLL cases.

Knowing what a smudge cell is, how do we handle them? Do we report the presence only? Do we count them? Or, do we ignore them entirely? Smudge cells are not skipocytes! For many years smudge cells were considered to be simply artifacts of slide making. More recently, studies have been conducted that show that there may be clinical significance to the number of smudge cells seen. While smudge cells are not diagnostic of CLL, it has been shown that, in newly diagnosed CLL, a larger percentage of smudge cells is a better prognostic factor. Patients with >30% smudge cells show longer times before requiring treatment and longer survival rates than patients with fewer smudge cells. These studies focused on vimentin, a protein that is important in lymphocyte cellular rigidity. Patients with low vimentin have more smudge cells and better survival rates.1,2

If we are performing a slide review, we are reviewing these slides because of some sort of instrument flag or rule trigger. There are several theories as to how smudge cells can be handled, and studies have been done to compare these theories.3 Laboratories have SOPs in place to guide technologist review and reporting, yet, I have noticed considerable variation in handling of smudge cells both within our lab and between labs. These pesky artefacts can be puzzling in both traditional (under the microscope) and digitized (CellaVision) microscopy and new technologists or unfamiliar operators can easily be misled. If we perform our manual differentials traditionally, under the microscope, we will no doubt notice the presence of smudge cells. It is important not to pass by these or consider them skipocytes. Some labs count these as their own category of cell and some labs merely report the presence of smudge cells. Other labs do not report smudge cells at all, with the exception being in known cases of CLL. In these CLL differentials, if the WBC count is very high, it may also be recommended to do a 200 cell differential. But, what happens when the manual diff doesn’t match the automated diff? The hematology analyzer will accurately count fragile cells, still intact in the specimen, and include them in the differential. If the cells then disintegrate on smear making, we see smudge cells on the slide. If we do not count these, this can affect the percentage of cell types in the differential, and potentially, in a patient with a low WBC, affect the absolute neutrophil count (ANC). If we are performing the manual differential (diff) in CellaVision, CellaVision identifies smudge cells and puts them in a separate category, but these are not reported as part of the diff. These are a ‘heads up’ to the technologist that further steps need to be taken to report out a differential. The importance of recognizing smudge cells is illustrated in Table 1 below for a patient sample with WBC 3.6 x 103/μL.

Table 1. Numbers of cells counted in three differentials on sample with WBC 3.6 x 103/μL.

The automated differential (auto diff) in this example, with 12% neutrophils counted, has an absolute neutrophil count of 432/ μL, which is considered critical (critical <500/μL). Fragile lymphocytes are intact in the blood sample and are counted by hematology analyzers.

The 200 cell manual differential above merely notes the presence of smudge cells, but no quantifier is given. The ANC here is not critical (774/μL) and the lymph% is only 61, possibly leaving the physician to question how many smudge cells were present, and what the true lymph% may be.

In the CellavVision differential in Table 1, based on 100 WBCs counted, the total percentages of Neuts is 20%, lymphs 61% and monos 19%. If an unexperienced tech did not notice or investigate the 68 smudge cells, the manual differential (manual diff) reported from the CellaVision would be very different from the auto diff, and has an ANC of 720/μL, above the critical range.

If however, the smudge cells in CellaVision were reported as a separate category, our differential would now be based on 168 cells counted. 100 WBCs counted plus the 68 smudge cells counted = total of 168 cells counted. Our neut% is now 11.9 (20/168*100), lymph % 36.3(61/168*100), monos% 11.3 (19/168*100) and smudge cell % 40.5 (68/168*100). This ANC matches that from the auto diff. And, if we further consider that the smudge cells are lymphocytes, this brings the count to 11.9% neuts, 77% lymphs and 11.3% monos. (68 +61 = 129/168*100 = 77% lymphs) which closely matches our automated differential.

Lastly, the ‘something else’, is that we can make an albumin smear on these specimens. It has been a practice in labs to perform a manual differential on an albuminized blood smear when a certain number, defined by SOPs, of smudge cells are seen. If this is your lab procedure, it is important to recognize the presence of smudge cells on the manual differential or CellaVision differential and take the steps to make an albumin smear. Adding a drop of albumin to a few drops of the patient blood can add protein to the specimen and prevent the formation of smudge cells. Table 2 shows the manual diff on the sample in Table 1, performed on the albuminized slide. Note that this eliminates the smudge cells and corrects the diff results to match the original automated differential.

Table 2. Albumin smear results on sample from table 1.

It can be seen from these examples, that the method of counting differentials with smudge cells can alter the results reported to the physician. Any of the differential methods above that count smudge cells give essentially the same results. If smudge cells are not counted, the lymphs will be under reported and the neutrophils will be over represented compared to the auto diff. Excluding smudge cells from the manual differential count or merely reporting their presence without quantification will also yield unreliable results, and then necessitates performing an albumin differential.

If we are to choose between an albumin differential and an automated differential, which studies have shown to be equivalent3, making and staining an additional smear is time consuming and can affect turnaround times. Thus, guidelines have been suggested that the first choice for handling pesky smudge cells is to review the smear and report the automated diff with a morphology comment that smudge cells are present. If automated diffs are not available, smudge cells should be counted as lymphocytes, or in a separate category4, as illustrated in Table 1. Study findings indicate that this method is sufficient for reporting a reliable manual differential on known CLL patients3. By counting smudge cells separately, however, as discussed previously, these numbers can be used in newly diagnosed cases of CLL as a prognostic indicator.

There is still debate on the value of reporting smudge cells on routine CBC smears. In most routine cases, an auto diff without quantitating smudge cells is considered sufficient. Pathologists, however, differ on whether smudge cells should be reported.

The best course of action is always to consistently follow your own lab’s SOPs, to be aware of flags, rules triggered and operator alerts with regard to smears, and to always be on the lookout for smudge cells. They are not skipocytes!


  1. Nowakowski GS, Hoyer JD, Shanafelt TD, et al. Percentage of smudge cells on routine blood smear predicts survival in chronic lymphocytic leukemia. J Clin Oncol. 2009;27(11):1844-1849.
  2. Amal Abd El Hamid Mohamed, Nesma Ahmed Safwat. New insights into smudge cell percentage in chronic lymphocytic Leukemia: A novel prognostic indicator of disease burden. The Egyptian Journal of Medical Human Genetics, 19 (2018) 409–415
  3. Gene Gulati, Vandi Ly, Guldeep Uppal, Jerald Gong, Feasibility of Counting Smudge Cells as Lymphocytes in Differential Leukocyte Counts Performed on Blood Smears of Patients With Established or Suspected Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma, Laboratory Medicine, Volume 48, Issue 2, May 2017, Pages 137–147, https://doi.org/10.1093/labmed/lmx002
  4. Denis Macdonald, MD, MBA, FRCPC, FCAP; Harold Richardson,et al. Practice Guidelines on the Reporting of Smudge Cells in the White Blood Cell Differential Count. Arch Pathol Lab Med—Vol 127, January 2003
  5. Luci Maria Sant’Ana Dusse; Tamiris Paula Silva, et al. Gumprecht shadows: when to use this terminology? J Bras Patol Med Lab, v. 49, n. 5, p. 320-323, 2013

-Becky Socha, MS, MLS(ASCP)CM BB CM graduated from Merrimack College in N. Andover, Massachusetts with a BS in Medical Technology and completed her MS in Clinical Laboratory Sciences at the University of Massachusetts, Lowell. She has worked as a Medical Technologist for over 30 years. She’s worked in all areas of the clinical laboratory, but has a special interest in Hematology and Blood Banking. When she’s not busy being a mad scientist, she can be found outside riding her bicycle.

Hematopathology Case Study: An 83 Year Old Man with an Elevated PTT

Case History

An 83 year old man with rapidly growing squamous cell carcinoma of the left temple and scalp underwent workup prior to surgery which showed an elevated PTT and a slightly elevated PT. The patient denied a history of abnormal coagulation tests or excessive bleeding or bruising. He also noted that he had previous surgeries including dental procedures without excessive bleeding. In addition, he did not have a history of clot formation.

Lab Values

Differential Diagnosis

At this point, the differential diagnosis for a prolonged PTT included the presence of an inhibitor (specific factor inhibiter vs. non-specific lupus anticoagulant) vs. reduced levels/activity of intrinsic pathway factors that would prolong the PTT, but would not significantly affect clot formation. This would include factors XI and XII. 

Additional Testing

An inhibitor screen/mixing study was performed and was positive. An inhibitor screen is performed by mixing the patient’s plasma with pooled normal plasma and running a PT or PTT.  If the PT/PTT corrects than the screen is negative. This means that a factor or factors were deficient in the patient’s plasma and were replaced with the pooled normal plasma resulting in a correction of the PT/PTT. In this case, a PTT at time 0 of 68 seconds and a PTT at 2 hours of 66 seconds was a failure to correct and indicated that an inhibitor was present, thus a positive result was entered.

The dilute Russell’s viper venom time (dRVVT) was used to test for a lupus anticoagulant. The screening test is performed by adding Russell viper venom, which directly activates coagulation factor X in the presence of calcium and a phospholipid poor reagent to the patient’s plasma and calculating time to clot. The confirmation test is the same assay with added excess phospholipid. In the presence of phospholipid dependent antibodies, the time to clot will be shorter for the confirmation test. The screen and confirmation ratios are normalized ratios (NR) of the patient sample result in seconds divided by the mean of the normal range in seconds. If the screen is <1.20, the confirmation test will not be run. If the screen is greater than 1.20 as seen here, the confirmation test will be run. The end result is reported as a normalized ratio of the screening test over the confirmation test. If the NR is greater than 1.20, than a lupus anticoagulant is reported as present.

Specific factor assays are performed by mixing the patient’s plasma with substrate plasma that is severely deficient in the factor being measured. Factor deficient plasma would be expected to give a prolonged clotting time. When patient plasma is mixed with factor deficient plasma, the clotting time will shorten and the degree of correction is proportional to the factor level in the patient’s plasma. The clotting times for the patient sample are compared to a reference curve. The reference curve is made with dilutions of normal plasma (containing 100% factor) added to factor deficient substrate plasma. All tests are run with 3 dilutions at 25%, 50% and 100% and curves are checked for parallelism errors, which might indicate the presence of an inhibitor. For this patient, factor XI was initially resulted as 1%, which would indicate a factor deficiency.

This is an example of a factor assay that shows parallelism. The reference plasma calibration curve and the patient plasma are parallel lines. 1


From the results, it initially appeared that there was both a lupus anticoagulant and a factor XI deficiency. However, it would be odd for a patient with no reported coagulation abnormalities to suddenly have both a lupus anticoagulant and a factor XI deficiency. The raw data from the factor XI assay was obtained.

Upon review, the factor XI assay did show parallelism errors. Parallelism is tested by performing serial dilutions of a standard with known normal concentrations of factor and recording the time to clot. This line is shown with the red arrow. In contrast, the patient sample appears to be a flat line that is not parallel to the calibration curve. Parallelism errors were flagged because from the 50% to 25% dilution, the corrected results more than doubled. If there is a >20% change between dilutions, this indicates possible interference and additional dilutions should be run to dilute out the inhibitor. The 25% dilution had a corrected result of 2.9, which was greater than a 20% increase from the 50% dilution result of 1.3. Once more dilutions were performed; the Factor XI level was ultimately close to 100%.

Additional factors were checked to see if they also increased with dilutions. This would add support to the theory of a non-specific inhibitor (lupus anticoagulant) that was affecting all of the factor levels, rather than a specific factor XI inhibitor or a concurrent factor XI deficiency. The curve from factor IX (below) showed a similar phenomenon. As the sample underwent additional dilutions, the corrected result increased significantly (from 12.8 at 50% to 26.8 at 25%). Ultimately, the factor level was close to 82%.

The curve from factor VIII also showed low results to begin with and ultimately normal levels with additional dilutions. Altogether, this supported the presence of a strong lupus anticoagulant that was non-specifically interfering with all of the factor levels and prolonging the PTT.


A prolonged PTT can be caused by many factors. In a patient without a bleeding history, lupus anticoagulant and certain factor deficiencies are high on the differential. The most common specific factor inhibitors are to FVIII and FIX. These generally arise in hemophilia patients treated with factor concentrates. It is very rare for a patient to develop an inhibitor to factor XI or XII.

Factor XI acts in the intrinsic pathway of the clotting cascade and is important for hemostasis. Deficiency of factor XI is rare and mainly occurs in Ashkenazi Jews. Generally, it does not cause spontaneous bleeding; however excessive blood loss can occur during surgical procedures.

Lupus anticoagulants are directed against proteins that complex with phospholipids. Although they prolong the PTT, they are associated with an increase in thrombosis rather than bleeding. In addition to interfering with the PTT assay, lupus anticoagulants may interfere with individual factor assays and result in non-parallelism (patient curve is not parallel to calibration curve) as seen in this patient. With increasing dilutions, the lupus activity will be disproportionately neutralized and the coagulation factor activity will increase in a non-parallel manner. 1

In a letter to the editor by Ruinemans-Koerts et al., they performed a set of experiments to investigate whether lupus anticoagulants vs. individual FVIII and FIX inhibitors can cause non-parallelism in the one-stage factor assay.  Non-parallelism was only detected using lupus sensitive reagents in plasma with high titers of lupus anticoagulants. The FVIII and FIX inhibitor containing samples both resulted in curves that were parallel to reference sample.

This curve shows that the factor IX inhibitor line is parallel to the reference plasma, while the lupus anticoagulant line is not. 1

Ultimately, this demonstrates the importance of running dilutions and being aware of parallelism errors when performing factor assays. This is especially important in patients with known or suspected lupus anticoagulants. In this case, the unlikely presence of a FXI deficiency with no previously reported coagulation testing abnormalities or bleeding history raised the suspicion of an inhibitor interfering with the factor assay. With a concurrent positive inhibitor screen and lupus anticoagulant test, as well as interference demonstrated with multiple factor assays, the best unified conclusion was a strong lupus anticoagulant. 1


  1. Ruinesman-Koerts, J., Peterse-Stienissen, I, and Verbruggen, B. ”Non-parallelism in the one-stage coagulation factor assay is a phenomenon of lupus anticoagulants and not of individual factor inhibitors. “ Letter. Thrombosis and Hemostasis, 2010, p.104.5.

Chelsea Marcus, MD is a Hematopathology Fellow at Beth Israel Deaconess Medical Center in Boston, MA. She has a particular interest in High-grade B-Cell lymphomas and the genetic alterations of these lymphomas.

Hematopathology Case Study: A 39 Year Old Woman Presenting with Persistent Cough and Pericardial Effusion

Case history

The patient is a 39 year old woman presenting with a persistent cough. Upon work up, a pericardial effusion is noted. Pericardiocentesis is performed and a smear made from the pericardial fluid reveals atypical lymphoid cells.

Cytology of the Pericardial Fluid

Image 1. Pericardial fluid cytology showing reactive mesothelial cells surrounded by benign small lymphocytes and atypical large lymphocytes.

Additional imaging reveals an anterior mediastinal mass measuring 12.6 cm. Excision of the mediastinal mass is performed. Sections of mediastinal mass show a variable population of lymphoid cells ranging from small to medium lymphocytes and some atypical large lymphocytes. These atypical large lymphocytes have irregular nuclear contours with abundant cytoplasm, vesicular chromatin and prominent nucleoli. These atypical large lymphoid cells are consistent with Hodgkin Reed-Sternberg cells. Abundant eosinophilic and scattered neutrophilic infiltration are noted within the nodules. These nodules are surrounded by dense collagen bands.

Image 2. H&E sections showing small to medium sized lymphoid cells with scattered large Hodgkin Reed-Sternberg cells infiltrating through fibrosis (frozen section A) and inflammatory cells predominantly eosinophilic infiltration (B) Fascin (C) and CD30 (D) are positive for atypical lymphoid cells.

Immunohistochemistry studies are performed, atypical large lymphoid cells are positive for CD30, Fascin and PAX5, while rare small to medium sized lymphocytes are positive for CD20, however, large atypical lymphoma cells are negative for CD20. Tumor cells are negative for CD3, CD5, CD15, LCA, ALK and EBER ISH. CD3 and CD5 highlight the reactive T cells in the background.

Image 3. PAX5 is positive in some tumor cells.

Overall, the case is consistent with nodular sclerosis classic Hodgkin lymphoma.  The presence of sheets of large lymphoma cells is suggestive of the syncytial variant.


Nodular sclerosis classic Hodgkin’s lymphoma (NSCHL) subtype has a distinct epidemiology, clinical presentation and histology. NSCHL is more common in females with peak aged between 15 and 34 years. The risk is higher in high socioeconomic status. The patients are presenting with particularly mediastinal mass and 40% B symptoms.

NSCHL can be distinguished from the other subtypes of Hodgkin’s lymphoma (HL) with characteristic histologic features. There is a nodular growth pattern and the nodules are surrounded by collagen bands representing nodular sclerosis.  The lymphoma is composed of variable number of Hodgkin Reed-Sternberg (HRS) cells, small to medium sized lymphoid cells and non-neoplastic inflammatory cells, predominantly eosinophils, neutrophils and histiocytes. HRS cells have multinucleated or binucleated with irregular nuclear contours and prominent nucleoli. HRS cells induce fibroblastic activity by expressing IL-13 and the fibrosis begins in the lymph node by invaginating into the lymph node along vascular septa.

Immunophenotypically, the lymphoma cells are mostly positive for CD30 and 75-85% positive for CD15. Association with EBV can be demonstrated with EBER in-situ hybridization.  The malignant lymphocytes in NSCHL are variably expressing CD20, PAX5 and CD79a, however, T cell antigen markers, particularly CD4 and CD2 are aberrantly expressed in NSCHL.

NSCHL is classified mostly as grade 2 and the prognosis is better than the other subtypes of HL.  Doxorubicin, bleomycin, vinblastine and dacarbazine (ABVD) is the most frequent induction regimen for NSCHL patients with over 70% response rate.

Patients with Syncytial Variant Nodular Sclerosis Classic Hodgkin Lymphoma experience a lower than expected rate of complete therapeutic response with shorter progression-free than non-SV NSCHL treated with standard therapy. Syncytial Variant NSCHL should therefore be recognized as a high-risk subgroup within the otherwise traditionally docile NSCHL classification. This case fits the classic presentation for syncytial variant with presentation as bulky (mediastinal) disease.


  1. Eberle FC, Mani H, Jaffe ES. Histopathology of Hodgkin’s Lymphoma. Cancer J. 2009 Mar-Apr;15(2):129-37.
  2. Swerdlow SH, Campo E, Harris NL et al. WHO Classification of Tumors of Haematopoietic and Lymphoid Tissues (Revised 4th Edition). IARC: Lyon 2017.
  3. Sethi T, Nguyen V, Li S, Morgan D, Greer J. Differences in outcome of patients with syncytial variant Hodgkin Lymphoma compared with typical nodular sclerosis Hodgkin Lymphoma. Ther Adv Hematol 2017, Vol. 8(1):13-20.

Ayse Irem Kilic is a 2nd year AP/CP pathology resident at Loyola University Medical Center. Follow Dr. Kilic on twitter @iremessa.

Kamran M. Mirza, MD, PhD, MLS(ASCP)CM is an Assistant Professor of Pathology and Medical Education at Loyola University Health System. A past top 5 honoree in ASCP’s Forty Under 40, Dr. Mirza was named to The Pathologist’s Power List of 2018. Follow him on twitter @kmirza