Hidden mastocytosis in acute myeloid leukemia with t(8;21)(q22;q22).

OBJECTIVES To assess the frequency of systemic mastocytosis (SM) in a large series of acute myeloid leukemia (AML) with t(8;21)(q22;q22). METHODS We retrospectively characterized 40 bone marrow aspirate smears and biopsy specimens from patients with AML with t(8;21) for the presence of SM. Cases were assessed for mast cell morphology and immunohistochemistry, as well as KIT exon 8 and 17 mutational assessment by reverse transcription polymerase chain reaction. RESULTS Four patients met criteria for SM, 1 met criteria for myelomastocytic leukemia, and 8 demonstrated the benign finding of mast cell hyperplasia. CONCLUSIONS We recommend examining all cases of AML with t(8;21) for the presence of SM via morphology, immunophenotyping, and KIT mutational analysis studies.