Benign Leukocytoses | Pathology Student

Hematopathology Quiz Part 2

Here is the second of three installments of a really nice quiz one of our readers sent (the first installment is here, and the third one is coming up). This is a quiz he recently gave to his residents (from medicine, pediatrics and pathology) rotating through hematopathology. Give it a try and see how many you get right! Make sure you check out the answers and nice explanations (if I do say so myself) at the end.

1. Smudge cells may be seen on the peripheral blood smear in which of the following?

A. Chronic lymphocytic leukemia
B. Chronic myeloid leukemia
C. Acute myeloid leukemia
D. Thalassemia

2. The erythroblasts in acute erythroleukemia (AML- M6) are usually positive for which of the following?

A. PAS
B. CD71
C. CD117
D. All of the above

3. The rare Bombay phenotype is seen in people who have blood type:

A. O
B. A
C. B
D. AB

4. Cryoprecipitate contains which of the following factors?

A. Factor VIII
B. Factor IX
C. Factor II
D. Factor VII

5. The major hematopoietic site in the human embryo is:

A. Spleen
B. Liver
C. Kidney
D. Yolk sac

6. POEMS syndrome includes all of the following EXCEPT:

A. Polyneuropathy
B. Ophthalmopathy
C. M-protein
D. Skin abnormalities

7. The most common class of immunoglobulin produced by the malignant cells in multiple myeloma is:

A. IgA
B. IgD
C. IgG
D. IgM

8. Which of the following is true with respect to hemophilia A?

A. Inheritance is autosomal dominant
B. It is more common in females
C. It never manifests before puberty
D. Patients are deficient in factor VIII

9. The cells of which of the following have a “fried-egg” appearance on bone marrow sections?

A. Hairy cell leukemia
B. Follicular lymphoma
C. Acute promyelocytic leukemia
D. Burkitt’s lymphoma

10. Which of the following immunophenotypic markers is a pan-B-cell marker?

A. CD3
B. CD19
C. CD33
D. CD56

Scroll down for the answers…

1. A. Smudge cells (also called ghost cells or basket cells) are actually damaged lymphocytes rather than a unique type of cell. Lymphocytes are more fragile than myeloid cells (like neutrophils) – so when you make a blood smear in a patient with a lymphoid disorder (like chronic lymphocytic leukemia), there are likely to be a bunch of smudge cells.

2. D. CD71 and CD117 are both erythroid markers. Erythroblasts in AML-M6 will often stain positively with the PAS (periodic acid schiff) stain (which stains glycogen and mucopolysaccharides). Normal erythroblasts are generally not PAS positive though.

3. A. People with the Bombay phenotype don’t make H antigen. What’s H antigen, you say? It is the antigen that you make first, before you create A or B antigens. To make A and B antigens, you start with a protein precursor (sticking out of the red cell membrane). You add fucose to make what’s called the H antigen. Then, if you have the A gene, you add N-acetylgalactosamine to the H antigen, which makes it an A antigen. If you have the B gene, you add galactose to the H antigen, which makes it a B antigen. If you don’t have either A or B (in other words, if you are type O), then you just leave the H antigen as is, and you don’t make either A or B antigens.

So…people with the Bombay phenotype do not make the H antigen (they stop at the protein precursor stage). They therefore don’t make A or B antigens, either (so they are type O). If a person with the Bombay phenotype needs a transfusion, you need to find Bombay blood – because if you give any other type (regular A, B, AB or O), that blood will have some H antigen in it, and the patient will bust open all those donor red cells (not a good thing to have happen!).

4. A. Cryoprecipitate is a plasma product that contains fibrinogen, von Willebrand factor, and factors VIII and XIII.

5. D. Ok, kind of a gimme.

6. B. POEMS is a rare syndrome that includes a plasma cell dyscrasia (usually myeloma) and a bunch of other stuff. The acronym covers some of the main features: polyneuropathy, organomegaly, endocrinopathy or edema, M-protein, and skin abnormalities (including hyperpigmentation and hypertrichosis). There are other potential complications, though – and not every patient with POEMS has all five features.

7. C. The most common class is IgG. The rarest is IgM. Some people argue that an IgM myeloma doesn’t exist; others say that it exists but is super super rare. Either way, if you get a plasma cell thing that expresses IgM, the first thing you should think of is Waldenstrom’s – myeloma would be way, way down on the list.

8. D. In hemophilia A, patients are deficient in factor VIII (in hemophilia B, it’s factor IX that is deficient). Inheritance is X-linked recessive (though up to 30% of cases arise spontaneously!). As any X-linked recessive disorder, it is more common in males. It often manifests in childhood.

9. A. The hairy cells in hairy cell leukemia have been described as having a “fried egg” appearance because they have these long cytoplasmic processes (“hairs”) that push the cells apart from each other. So the little cell nuclei look like the yolks of eggs, with egg whites (cytoplasm) around them.

10. B. CD19 is a marker present on most B cells (so it’s a “pan” B-cell marker). CD3 is a T-cell marker; CD33 is a myeloid cell marker, and CD56 is a natural killer cell marker.

Why you need to look at absolute numbers (not just percentages) of white cells

Q. I need help with this question from Robbins:

15 year old boy with fever of 10 days. Petechial hemorrhages on trunk and extremities. CBC shows Hg 13.2, Hct 38.9%, MCV, 93, plt ct 175,000 and WBC ct 1860 with 1% segs, 98% lymphs, and 1% monocytes. BM biopsy shows no abnormal cells. What’s the diagnosis?

The answer was overwhelming bacterial infection! It said you are supposed to multiply the percentages in the differential by the total WBC to get absolute values.Â Any tips for reading WBC counts and diffs? They are so daunting! Would it possibly be included in The Complete But Not Obsessive Hematopathology Guide?Â I’ve definitely gotten some questions right just from reading pathologystudent though! Such as the difference between a CML and leukomoid reaction! 🙂

A.Â This is a great question! Yes – there is quite a bit about the diff in The Complete Hematopathology Guide. You might just start by downloading theÂ Top 10 AnemiasÂ if you haven’t already (it’s free) – I have a bit in there about normal CBC values.Â I think once you understand the diff and the CBC, it becomes a lot less overwhelming. You do need to know how to multiply the percentages to get the absolutes…but you definitely don’t have to do that on every case. And for most cases, it’s fine to just do a ballpark figure.

Why do you need to look at absolute counts?
The reason you need to look at absolute counts is because if you just look at percentages, you could mess up.Â Let’s say you have 60% neutrophils in a particular patient. You might take a quick look at that and go, oh, yeah, that looks fine. But if you don’t take the time to find out the absolute neutrophil count, you could be missing something. If the WBC count in that particular patient is very low, say 1.5 (normal being 4-11), then the patient would have a low number of neutrophils even though theÂ percentageÂ of neutrophils is normal.

Conversely, if the same patient had a very high WBC (say 120), then 60% of the total WBC would be a very high number! Higher than normal for sure. So if you just looked at the percentage of neutrophils in that case, you’d go okay, that looks normal – when in fact the number of neutrophils would be very elevated.So that’s the theory behind looking at the absolute numbers. In reality, most of the time you can just take a look at the WBC, and if it’s really high or low, then go ahead and figure out the absolute numbers of the individual white cells (by multiplying the percentage of that particular cell times the actual WBC). If the WBC is normal, or pretty close to normal, you probably don’t need to go to that amount of work.

Neutropenia and infection
The Robbins question is trying to get you to a) recognize that the patient is neutropenic (in addition to being leukopenic overall), and b) figure out that the reason the neutrophil count is so low is because the patient has a massive infection, and the neutrophils are leaving the bloodstream to go the tissues where they are needed (hence the number of neutrophils in the blood is actuallyÂ low). Usually in an infection (a bacterial one anyway), the WBC is high, and the percentage (or at least the absolute number) of neutrophils is way increased. This leaving-the-bloodstream phenomenon that happened in this patient is uncommon – but it does occur.

By the way, if you just looked at the % of lymphocytes in this question, and didn’t think too much about the WBC, you might (incorrectly) conclude that the patient has a lymphocytosis (98% lymphocytes! That sounds like a lot.) In fact, the patient is actually leaning towards being lymphocytopenic (since the total number of white cells is really low). The normal absolute lymphocyte count is somewhere between 1 and 4; in this patient, it’s about 1800 (98% of 1860).

Hope that helps! I hope you can get to the point where it doesn’t feel totally overwhelming – because it’s actually pretty straightforward and doable, once you understand some general principles.

Leukoerythroblastotic reaction

Here’s a long term: leukoerythroblastotic reaction. Despite its length, it’s a pretty good term, because it describes a reactive condition in which you see young red cells (erythroblasts) and young white cells (leuko-) out in the peripheral blood. (more…)

Mono vs. acute leukemia

Q. I’m a medical student, and I wonder if you have some good tips about how to tell tell apart mononucleosis from AML on a blood smear? (more…)

It’s here!

The Complete (but not obsessive) Hematopathology Guide – is here! Check out the cover at the left – click on it, and you’ll be taken to a page that describes the guide and has a place to order. (more…)

New study guide coming!

I’m putting the final touches on a new study guide!

This one is a complete hematopathology guide that covers everything you need to know for medical (and dental) boards. (more…)

How to identify lymphocytes in a blood smear

Q. Currently I am in a residency course to finish up my training as a medical laboratory technician; for the next two weeks I’ll be doing nothing but cell differentials in the hematology lab. Today as I was skimming the abnormal slides I found that I was having some difficulty distinguishing lymphocytes (particularly plasmacytic lymphs) from plasma cells found in the peripheral blood. Any pointers? In addition, I’m having a similar issue making the distinction from activated lymphocytes and monocytes. Pesky lymphs…

A. Those are very legitimate questions and ones that trouble even people with lots of experience from time to time. The key to both of these problems (and most problems where you’re trying to distinguish one cell from another) is to look at the chromatin.

1. Lymphocytes vs. plasma cells vs. plasmacytoid lymphocytes

Lymphocyte chromatin has a unique look in that it is clumpy and smudgy at the same time. Check out the top photo of normal lymphs – there are light and dark areas (clumping) within the chromatin, but the distinction between the two is not sharp (it’s smudgy). It’s like you licked your thumb and smudged the chromatin. Okay, that’s a weird analogy, but whatever. Plasma cell chromatin is blocky and discrete; it is sometimes arranged in a “clock-face” pattern around the edge of the nucleus. Not smudgy. Plasmacytoid lymphs have the chromatin of a lymphocyte (clumpy and smudgy) but the cytoplasm of a plasma cell (eccentric nucleus with a clearing where the golgi apparatus is).

2. Reactive (activated) lymphocytes vs. monocytes

Reactive lymphocytes – particularly big ones – can look a lot like monocytes. Again, the key is to look at the chromatin. Large reactive lymphocytes are usually immunoblasts, and as such, they have a big nucleolus (or two). In the bottom photo, there is a big reactive lymphocyte (called a Downey 3 cell) on the right. These cells also have fine chromatin (it has to be fine, or you wouldn’t be seeing the nucleolus). Monocyte chromatin is more dense (no nucleoli) and has a “raked” appearance. It is like you dragged a tiny garden rake across the nucleus. Also, the nucleus is often kidney-bean or horse-shoe shaped, or at least has a nice indentation or two. In addition to the chromatin differences, there are cytoplasmic differences (though these are less consistent): monocyte cytoplasm is typically dishwater grey with tiny dust-like granules, whereas reactive lymphocyte cytoplasm is usually light blue (either pale light blue or a relatively bright light blue) and if granules are present, they tend to be larger.

It just takes time and practice. Show everything you’re wondering about to someone who’s been in the lab a while – that’s the best way to learn. Most techs – as you no doubt know – are really nice and very knowledgeable!