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Chapter 15: Hematopathology

A 34-year-old woman with no significant past medical history presents with fatigue. A CBC is obtained and is notable for microcytic anemia, mild thrombocytopenia, and blasts identified on a PB smear (12% of total nucleated cells by manual differential). Flow cytometry is performed on PB and reveals abnormal myeloid blasts. A BM biopsy is performed and demonstrates trilineage hematopoiesis with the following differential: 14% blasts, 5% promyelocytes, 9% myelocytes, 38% maturing granulocytes, 26% erythroid, 4% lymphocytes, 2% monocytes, and 2% eosinophils. Cytogenetic analysis demonstrates two clonal cytogenetic abnormalities, specifically a deletion 9q and t(8;21)(q22;q22.1) with a RUNX1-RUNX1T1 fusion transcript identified by molecular testing. What is the best diagnosis for this patient?

A. Myelodysplastic syndrome with excess blasts

B. Acute myeloid leukemia

C. Acute promyelocytic leukemia

D. Chronic myeloid leukemia

E. Reactive blast proliferation

Answer: B

Explanation: This case highlights that a minimum blast requirement (generally 20%) is not required for the diagnosis of AML in the setting of specific cytogenetic abnormalities, including t(8;21)(q22;q22.1). In this case, the presence of an abnormal elevated blast population with the aforementioned cytogenetic abnormality is diagnostic of AML with a recurrent cytogenetic abnormality. Acute promyelocytic leukemia with PML-RARA and AML with inv(16)(p13.1q22) or t(16;16)(p13.1;q22); CBFB-MYH11 can also be diagnosed without regard to blast count. Chronic myeloid leukemia is characterized by a Philadelphia chromosome with t(9;22)(q34.1;q11.2) and BCR-ABL1 fusion.

A 12-year-old boy presents with several weeks of fatigue, fever, and rapid-onset cervical lymphadenopathy. A CBC is unremarkable. An excisional lymph node biopsy demonstrates diffuse effacement of the lymph node by a monomorphic population of somewhat polygonal intermediate-size lymphocytes with frequent mitotic figures, apoptotic bodies, and scattered histocytes containing cellular debris within their cytoplasm. Flow cytometry of the lymph node specimen reveals that 87% of analyzed cells represent a clonal population of mature B-cells with the following immunophenotype: CD5-, CD10+, CD19+, CD22+, CD34-, CD38+ and negative for other analyzed markers (including T-cell markers). Immunohistochemical staining of the lymph node shows that the monomorphic lymphocytes have a Ki-67 proliferation rate of nearly 100% and overexpress the MYC protein with no staining for TdT. EBV by in situ hybridization is negative. By cytogenetic analysis, there is a t(8;14) with an MYC translocation demonstrated by FISH. What is the diagnosis?

A. B-lymphocytic lymphoma

B. T-lymphoblastic lymphoma

C. Follicular lymphoma

D. Burkitt lymphoma

E. Large B-cell lymphoma

Answer: D

Explanation: The described morphology is ...

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