Two color flow cytometric analysis of concomitant acute myeloid leukemia and chronic lymphocytic leukemia.

During evaluation for macrocytic anemia and thrombocytopenia, a 74-year-old female was found to have a leukocytosis with two apparent populations of malignant cells identified in her peripheral blood smear and bone marrow aspirate. Morphologic characteristics of the two cell types were unusual, and cytochemical assays yielded ambiguous results. Two-color flow cytometric analysis demonstrated two distinct cell populations with immunophenotyping patterns consistent with chronic lymphocytic leukemia (CD5+/CD20+) and acute myelocytic leukemia (CD33+/CD34+), detected concurrently. The concomitant appearance of CLL and AML has been reported only rarely. The use of two-color flow cytometry to differentiate the populations demonstrates the utility of this technology in resolving unusual hematological malignancies.