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Acute biphenotypic leukemia
CS Chim, SK Ma*
University Departments of Medicine and Pathology*, Queen Mary Hospital, University
of Hong Kong, Hong Kong.
Correspondence: DR CS Chim, Honorary Clinical Associate Professor, Department
of Medicine, Queen Mary Hospital, Hong Kong. Tel: (852)28554776. Fax: (852)29741165.
Email: jcschim@hkucc.hku.hk
A 60-year-old man presented with symptomatic anemia and a right inguinal
lymph node enlargement for 2 weeks. Complete blood count showed: hemoglobin
7.2 g/dL, platelet count 63 x 109/L, and leukocyte count 67 x 109/L
with 80% being blast cells. Inguinal lymph node biopsy confirmed leukemic infiltration.
Bone marrow examination showed hypercellular marrow with blast cells accounting
for 90% of all nucleated cells. Morphologically, two populations of blast cells
were present: hand-mirror cells and regular myeloid blasts (Figure 1A). Multiple
Auer rods were identified in myelocytes (Figure 1B). Despite the presence of
two discrete morphologic populations, both hand-mirror cells and myeloblasts
were positive for myeloperoxidase by cytochemistry (Figure 1C), thereby suggesting
the same clonal origin. This is further supported by the dual expression of
CD2 (T-cell marker) and CD117 (myeloid marker) in the majority (70%) of blasts
(Figure 1D). Therefore, the overall pathologic features were consistent with
acute biphenotypic leukemia with blasts showing myeloid and T-lymphoid characteristics.
Karyotyping of bone marrow cells showed 46,XY. the patient achieved complete
remission with cytarabine and idarubicin.
A. Bone marrow smear showing replacement of normal hematopoietic elements by blasts, including many hand-mirror cells, and B. multiple aver rods in a mmyelocyte (Wright-Giemsa x 1000). C. Cytochemical staining for myeloperoxidase, showing positive reaction in the form of black granules in both hand-mirror cells and large blasts. D. Flow cytometric analysis of blast cell immunophenotype, showing dual expression of CD2-FITC and CD117-PE on the blast population (in quadrant 2 of the diagram)
