MEDizzy - A 5-year-old boy has become increasingly lethargic for the

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Combined Hematology II

A 5-year-old boy has become increasingly lethargic for the past 2 months. On physical examination his temperature is 37.3 °C. There are ecchymoses noted on the skin of his lower legs. Laboratory studies show Hgb 9.2 g/dL, Hct 27.8%, MCV 91 fL, platelet count 101,000/microliter, and WBC count 12,128/microliter. A bone marrow biopsy is performed and on microscopic examination shows nearly 100% cellularity with replacement by primitive cells that have large nuclei with delicate chromatin and indistinct nucleoli with scanty cytoplasm. These cells mark for CD10 (CALLA) antigen. Which of the following is the most likely diagnosis?

ExplanationC. The morphological description of primitive cells in the bone marrow is suggestive of blasts which are positive for CD10 which gives the diagnosis of ALL. In some studies, ALL has been subdivided into CD10 (the common acute lymphoblastic leukemia antigen, abbreviated (ALLa) positive and CD10 negative. The majority of B-lineage ALL cases express CD10. In B-lineage ALL, the percentage of cells expressing CD10 decreases in more mature forms. Positive CD10 expression is associated with favorable clinical outcome.