Acute lymphoblastic leukemia in a patient with longstanding polycythemia vera: cytogenetic analysis reveals two distinct abnormal clones.

A 68-year-old female patient is described in whom acute lymphoblastic leukemia followed a long course of polycythemia vera. Chromosomal analysis of a peripheral blood specimen at the time of blastic transformation revealed two distinct clones: one characterized by a chromosomal abnormality frequently noted in polycythemia vera and the other by a rearrangement characteristically observed in lymphoid malignancies. These findings suggest the existence of two independent hematologic diseases: this phenomenon would not support the speculation from previous reports that lymphoproliferative disorders in patients with polycythemia vera arise from clonal evolution.