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Discussion Starter · #1 ·
A mother brings her 6-year-old son to his pediatrician because he has been having recurrent nosebleeds. Physical examination reveals diffuse petechiae. Laboratory studies show

Complete blood count
Hemoglobin 9.0 g/L
Platelet count 20000/mm3
Leukocyte count 14500/mm3

Purple Textile Organism Violet Pink

click image to enlarge

Bone marrow aspiration reveals the following:
The large cells at the center of the slide demonstrate positive immunostaining for terminal deoxy nucleotidyltransferase (TdT). They express surface CD19 and CD1O as well. What is the most likely diagnosis?

A. Precursor B-cell leukemia
B. Precursor T-cell leukemia
C. Mature B-cell leukemia
D. Mature T-cell leukemia
E. Hodgkin's lymphoma

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C. mature B-cell leukemia.

if surface markers present, its mature B- ALL,
if cytoplasmic markers present, its pre B-ALL.
CD markers are extremely useful in diagnosing both leukemia and lymphomas, if less than 10-T cells, if 10 or greater than 10- B cells.
Isn't TdT a marker for precursor lymphocytes? Maybe A? :notsure:

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487 Posts
Discussion Starter · #8 ·
A) Precursor B-cell leukemia

The correct ans is A) Precursor B-cell leukemia

Mondoshawan, Pav10, drahmednawaz, apx85 and mle2resident are chosen the correct answer.

The above bone marrow smear shows several lymphoblasts with a high nuclear-to-cytoplasmic ratio, variably condensed nuclear chromatin, and prominent nucleoli. The presence of these immature cells excludes choices C, D & E. The differential diagnosis of this acute lymphoblastic leukemia CALL) includes precursor B-cell leukemia (precursor B-ALL) and precursor T-cell leukemia (precursor T-ALL).

Precursor B-ALL and precursor T-ALL can be distinguished from each other only by immunophenotyping. Lymphoblasts in precursor B-ALL are positive for TdT, CD1O, and almost always for CD19. In contrast, lymphoblasts in precursor T-ALL are TdT positive and variably express CD1a and the T cell markers CD2, CD3, CD4, CD5, CDT and CD8.

ALL is primarily a disease of children (75% occurs in children under six years of age). Most patients with precursor B- ALL present with evidence of bone marrow failure: thrombocytopenia and/or anemia and/or neutropenia. The leukocyte count may be normal, decreased or increased.
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