T-lymphoid extramedullary (lymphadenopathic) blast crisis in CML.

T-cells are only rarely involved in chronic myeloid leukemia. We report an unusual case of T-lymphoid extramedullary (lymphadenopathic) blast crisis in a 66-year-old patient with Philadelphia positive chronic myeloid leukemia. The lymph node morphological picture resembled that of a peripheral T-cell lymphoma. Immunohistochemical stainings showed most lymph node blasts to have T-phenotype (positivity for CD-2, CD-3 and CD-5). Flow cytometric phenotyping confirmed T-phenotype, with positivity for CD-7, CD-38 and TdT. Cytogenetic analysis of lymph node cells revealed Philadelphia chromosome with an additional chromosomal abnormality (add(6p)). The BCR-gene rearrangement in the lymph node blasts was identical to that in the bone marrow. This case adds to the growing evidence that CML may be a disorder of the common stem cell from which T-, B- and myeloid progenitors originate.