Philadelphia-chromosome-positive pre-B-cell leukemia presenting as blast crisis of chronic myelogenous leukemia.

Cytogenetic studies of chronic myelogenous leukemia (CML) have shown that the majority of hemopoietic cells originate from pluripotential stem cells affected in this disease. Evidence that lymphocytes are also progeny of these stem cells, however, has been indirect. Philadelphia-chromosome-positive leukemic blasts from a 4 10/12-yr-old boy with CML in blast crisis had features characteristic of pre-B leukemic cells, including expression of cytoplasmic IgM and absence of surface immunoglobulin. Additional immunologic, enzymatic, and pharmacologic characterization of these cells supported their pre-B-cell phenotype. Together, these features provide direct evidence for CML stem cell ancestry to lymphocytes of the B-cell lineage.