Pan myeloid antigen-negative pediatric acute megakaryoblastic leukemia.

Acute megakaryoblastic leukemia (AMKL) is a relatively common type of acute myeloid leukemia in children. We describe two unusual cases of AMKL that by flow cytometry (FC) lacked expression of any commonly evaluated myeloid antigens. One case presented as a periorbital myeloid sarcoma and clinically was thought to be a solid tumor. In both cases, the leukemic blasts were variably positive for the megakaryocytic marker CD61. Cytogenetics confirmed the presence of the t(1;22) in one case. Cytogenetics and inclusion of megakaryocytic markers in FC panels when evaluating pediatric specimens is critical for appropriate diagnosis for myeloid antigen negative AMKL.