Mantle cell leukemia as a cause of leukostasis

A 72-year-old man was admitted with hypoxemic respiratory distress. Given a white blood cell count of 600 × 10 9 /L and symptoms of leukostasis, emergency leukapheresis was initiated. The white blood cell count immediately after the first leukapheresis was paradoxically increased to over 700 × 10 9 /L. Peripheral blood smear findings showed morphologically immature mononuclear cells and numerous circulating mitotic figures. Initial flow cytometry results showed a lambda light chain-restricted B lymphoid population positive for CD20, CD19, CD5, and FMC-7, and negative for TdT, CD10, CD23, CD34, CD117, and myeloid markers, suggesting classification as a blastoid variant of mantle cell lymphoma in a leukemic phase. Subsequent testing using DNA fluorescence in situ hybridization was positive for t(11;14), confirming the diagnosis of mantle cell leukemia. Although mantle cell lymphoma occasionally transforms or can even present as leukemia (leukocytes .40 × 109/L), it is rare for it to present with such profound leukocytosis and an overwhelming number of pleomorphic/blastoid forms. Although morphology suggested acute lymphoblastic leukemia, a more specific diagnosis of blastoid variant mantle cell lymphoma was obtained in 12 hours by applying complementary techniques of flow cytometry and rapid cytogenetics.