Here is the final installment of a really nice quiz one of our readers sent (check out the first and second installments). This is a quiz recently given to medicine, pediatrics and pathology residents 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. A 24-year-old female presents with prolonged PTT which did not correct following incubation for 2 hours with control plasma. Which of the following is the most likely diagnosis?
6. The leukemic cells in large granular lymphocyte leukemia are positive for:
B. CD 117
C. CD56 D. CD34
7. A 65-year-old female presents with fatigue. A blood smear shows abnormal lymphocytes, which are positive for CD5, CD19, and CD20, but negative for CD23. Cytogenetic analysis reveals a t(11;14). What is the diagnosis?
A. Hairy cell leukemia
B. Mast cell leukemia
C. T-cell acute lymphoblastic leukemia
D. Biphenotypic leukemia
Scroll down for the answers…
1. B. If you have a prolonged PTT, and you’re wondering what the cause is, one thing you can do is a mixing study , which is what this question is getting at. In a mixing study, you add a little normal plasma to the PTT (along with the patient sample) and then run the PTT again. If it “corrects” (meaning that the PTT is now normal), then it means the patient was missing something that the normal plasma provided (usually the thing that’s missing is factor VIII or IX). If it doesn’t correct (meaning that the PTT is still prolonged), then there is something in the patient sample that is inhibiting the test (usually the thing that’s inhibiting the test is an antiphospholipid antibody ). So for the answers to the question: the correct answer is B (since the PTT didn’t correct). In hemophilia A, a mixing study would make the PTT correct, so A is wrong. Patients with factor V Leiden or von Willebrand disease don’t have a prolonged PTT, so C and D are wrong.
2. C. A “dry tap” means that you get the needle in the marrow cavity, and when you pull back on the syringe, no marrow is drawn out. This usually means that there is fibrosis in the marrow, which is something you can see in pretty much any myeloproliferative disorder, particularly in the end stages (so A and D could produce a dry tap). In hairy cell leukemia (B), there are little threads of fibrosis surrounding each hairy cell. It gives the marrow a “chicken-wire” appearance. Patients with ITP (C) don’t have fibrosis in the marrow. The problem in ITP is that the body is attacking its platelets – it has nothing to do with fibrosis in the marrow – so C is correct.
3. A. All-trans-retinoic acid (ATRA) is a treatment that was developed for acute promyelocytic leukemia (APL). In APL, the retinoic acid receptor is screwed up, and the malignant cells get “stuck” in the promyelocyte stage. This is not good, because if you give a patient with APL regular chemotherapy, which tends to bust open cells, you’ll release all the promyelocyte granules (which contain pro-coagulant substances), putting the patient at risk for disseminated intravasular coagulation. ATRA overcomes this maturation block, allowing the malignant promyelocytes to mature into myelocytes, then metamyelocytes, then neutrophils. Then you can give the patient regular chemotherapy without the risk of DIC. ATRA doesn’t work in any of the other leukemias listed, because those leukemias don’t have a problem with the retinoic acid receptor.
4. A. Supravital staining means that you do the stain on liquid (not fixed and dried) blood. Supravital stains are used only in certain settings, like when you’re looking for Heinz bodies, or when you’re counting reticulocytes (polychromatophilic cells). The supravital stain used to stain polychromatophilic cells is new methylene blue (A).
5. B. Both Glanzmann thrombasthenia and Bernard-Soulier syndrome are hereditary platelet disorders in which platelet receptors are deficient or defective, and patients bleed excessively. In Glanzmann, IIb-IIIa is deficient, meaning that the platelets can’t bind fibrinogen very well, which means they can’t aggregate well. In Bernard-Soulier, Ib is abnormal (meaning that platelets can’t bind von Willebrand factor very well, and can’t adhese to the subendothelium very well). It turns out that patients with Bernard-Soulier (but not Glanzmann) have big platelets, too. So B is correct. Big platelets are not seen in von Willebrand disease (C) or TTP (D).
6. C. The lymphocytes in large granular lymphocyte leukemia are T cells. They are typically positive for CD8, CD 16, and CD56 or CD57. CD33 (A) is a marker seen mostly on myeloid cells. CD117 (B) is present on hematopoietic stem and progenitor cells, and CD34 (D) is present on hematopoietic stem cells, endothelial cells, mast cells and some dendritic cells.
7. B. The t(11;14) is characteristic of mantle cell lymphoma, and not of any of the other types of lymphoma listed. Also, mantle cells tend to be CD5, CD19 and CD20 positive, but CD23 negative. The cells of hairy cell leukemia (A), marginal zone lymphoma (C) and CLL (D) have different immunophenotypes.
8. B. Mast cells contain tryptase (which is a serine protease) in their little granules. Hairy cells (A), T-cell ALL (C) cells, and the cells of biphenotypic leukemia (D) are all negative for tryptase.