Acute myeloid leukemia with unusual mature lymphoid-like morphology in a subset of blasts.

We report a case of newly diagnosed acute myeloid leukemia with atypical blast morphology. Peripheral blood smear showed an atypical, dimorphic population of myeloblasts, including a subset with typical morphology and a separate subset with unusual mature lymphoid-like morphology. Flow cytometric immunophenotyping was crucial in characterizing the dimorphic population as a single myeloid blast population.