Biphenotypic (mixed myeloid/T-cell) extramedullary myeloid cell tumor

A 32-year-old male with a 4-year history of chronic myelogenous leukemia (CML) in chronic phase for 4 years, then myeloid blast crisis for 7 months, developed diffuse bulky lymphadenopathy in association with a white blood count (WBC) of 17,100/mm3 with 70% blasts. Biopsy of a cervical lymph node revealed a blastic extramedullary myeloid cell tumor, which showed a biphenotypic (mixed myeloid/T-cell) immunophenotype. Chromosomal analysis revealed karyotypic features of both myeloid and lymphoid lineages. Although extramedullary myeloid cell tumor (EMT, granulocytic sarcoma, chloroma) is well known to occur in chronic myelogenous leukemia (CML), to our knowledge this is the first description of evolution of CML into a biphenotypic EMT.