Bilineage acute leukemia of T-lymphoid and myeloid lineages.

We report the case of a child with Philadelphia chromosome-negative bilineage leukemia characterized by the coexistence of T-cell leukemia and myelomonocytic leukemia. Comparative analyses of genetic markers and proliferative/differentiative potential show the possibility of malignant transformation of a T-lineage stem cell with the potential to differentiate into the myeloid lineage.