A 68-year-old woman presented with a 6-week history of generalized fatigue, decreased appetite, profound all-day sweating, and 40-pound weight loss. Physical examination revealed no lymphadenopathy or hepatosplenomegaly. Laboratory test results showed normocytic anemia with normal WBC and platelet counts. Magnetic resonance imaging revealed heterogeneous mixed T1 and T2 signal changes but with no solid mass. A bone marrow aspirate showed many blasts with dispersed chromatin and scanty deeply blue cytoplasm containing numerous vacuoles (panel A, Wright-Giemsa stain; original magnification ×1000). Results of marrow biopsy revealed sheets of blasts with a starry sky pattern (panel B, hematoxylin and eosin stain, original magnification ×400; insert, CD20 stain by immunohistochemistry, original magnification ×400). Using flow cytometry, a B-lymphoid blast population showing low side scatter and dim CD45 characteristics, and expressing CD19, CD20, and CD10 with a subset of terminal deoxynucleotidyltransferase but complete absence of surface light chains, was detected; this was consistent with immature B-cell phenotype (panel C). However, strong positivity for Epstein-Barr virus (EBV) by EBV-encoded small RNA (EBV latency-1 infection) (panel D, EBV in situ hybridization; original magnification ×400) and solo c-MYC gene rearrangement by fluorescence in situ hybridization analysis (panel D, insert, c-MYC break apart probe, original magnification ×1000) supported the diagnosis of Burkitt leukemia.
Burkitt leukemia is an extremely rare mature B-cell neoplasm recognized by the recent World Health Organization classification as a leukemic variant of typical Burkitt lymphoma. However, a study recently showed that Burkitt leukemias with immature B-cell phonotype that mimic precursor B-acute lymphoblastic leukemias are molecularly distinct from Burkitt lymphomas.