Leukemia cutis in blastic transformation of chronic myelocytic leukemia: TdT positive blasts and response to vincristine and prednisone.

A patient with chronic myelocytic leukemia (CML) in blast transformation with extensive involvement of the skin is reported. The leukemic infiltrates consisted of blasts with lymphoblastoid morphology which were positive for terminal deoxynucleotidyl transferase (TdT) by fluorescent assay. The infiltrates rapidly resolved with vincristine and prednisone therapy. Similar recurrence 4 and 8 months later responded as dramatically to the same therapy and to cytosine arabinoside. This unusual case of extensive leukemia cutis supports the evidence that patients in blast crisis with TdT positive cells are responsive to vincristine and prednisone. The implications of this case in terms of the origin of these cells based upon morphology and TdT content, as well as the diagnosis and therapy, are discussed.