Acute lymphoblastic leukemia followed by chronic myelocytic leukemia.

Second hematologic malignancies occur rarely in patients previously treated for leukemia. This report describes a patient with acute lymphoblastic leukemia who remained in complete remission for 5 yr and then developed chronic myelocytic leukemia (CML). The original lymphoblasts were associated with a partial deletion of chromosome 21, while CML was associated with a classic Philadelphia marker, indicating the independent origin of the two leukemias.