demonstrating a wide range of RBC sizes. Poikilocytosis, or differently shaped
RBCs, is also incorrect because the shape of the RBCs in this peripheral smear is
uniform. Spherocytes, as in hereditary spherocytosis, do not have any areas of
pallor when examined on a peripheral blood smear; this is not descriptive of the
cells pictured here. Basophilic stippling, in which dark, punctate dots are contained
within the RBC, is not seen here. Consistent with liver disease, this man also has a
mild macrocytosis and mild pancytopenia (often caused by splenomegaly).
Q.4. A 62-year-old man without a significant past medical history comes in for his
yearly physical. He has no complaints. On physical examination, everything is
normal except for some mild right axillary adenopathy. You also note
splenomegaly. Concerned, you order a CBC, which shows a WBC of 30,000,
hematocrit of 37% (MCV is 88), and platelet count of 140,000. Reviewing lab data
from previous examinations, you note that his WBC five years ago was 15,000,
and two years ago was 18,000. His peripheral blood smear is shown in Figure
52Q-6. What is the most likely diagnosis?
A. Vitamin B
12
deficiency
B. Mononucleosis (Epstein-Barr virus infection)
C. Acute myelogenous leukemia (AML)
D. Chronic lymphocytic leukemia (CLL)
E. Essential thrombocytosis (ET)
Answer: D. The peripheral blood smear in this case shows a predominance of
lymphocytes, with their characteristic small size and thin rim of cytoplasm, which
correlates with the report of an elevated WBC. Noted on this slide are “smudge
cells,” commonly seen in CLL. With vitamin B
12
deficiency, we would expect to see
hypersegmented polymorphonuclear cells (i.e., 5% of the cells with 5 lobes or
greater), which are absent from this blood smear. Mononucleosis results in
“atypical” lymphocytes with large, open nucleoli. AML is unlikely; clinically, the
patient has a chronic elevation of his WBC and his peripheral blood smear shows
small, compact lymphocytes, not an increase in immature blasts. With essential
thrombocytosis, large numbers of platelets should be seen. Both the report of his
CBC and his peripheral blood smear fail to demonstrate an elevated platelet count.
Q.5. An 80-year-old man presents with six months of fatigue and is found to have
pancytopenia. Other laboratory data, including liver function tests, are normal. On
physical exam he is found to have marked splenomegaly without other significant
lymphadenopathy. His peripheral blood smear reveals numerous lymphocytes with
projections, and you suspect hairy cell leukemia. Confirmation of the diagnosis can
be made by
A. Bone marrow aspirate