Evolution of complex chromosomal rearrangements in a case of biphenotypic pre-B/myeloid acute leukemia.

A case of acute biphenotypic leukemia, in which blast cells coexpress antigens of both lymphoid and myeloid lineages, was seen in a 24-year-old female. The clonal karyotype was complex but did not include any of the abnormalities previously found in biphenotypic leukemia. Chromosome abnormalities included breakpoints seen in both acute lymphoblastic and acute myeloid leukemias as well as a number of known fragile sites, namely the rare heritable fragile site at 10q24, and the common, aphidicolin-induced sites on chromosome 7.