Promyelocyte morphology. Differentiation of acute promyelocytic leukemia from benign myeloid proliferations.

Bone marrow aspirates from patients with acute agranulocytosis or a marked left shift in myeloid maturation can mimic acute leukemia, particularly acute hypergranular promyelocytic leukemia. Bone marrow aspirates from 16 cases of apparent acute promyelocytic leukemia, 4 cases of acute agranulocytosis, and 1 case of a marked myeloid left shift were studied for the presence or absence of differentiating features. Normal or reactive promyelocytes were characterized by prominent paranuclear clear Golgi zones, whereas promyelocytes from true leukemic cases all had heavy azurophilic granules dispersed diffusely throughout the cytoplasm. Prominent Golgi zones in promyelocytes were associated only with benign myeloid conditions and were not observed in acute promyelocytic leukemia. The presence of prominent clear Golgi zones in promyelocytes is an important feature assisting in the distinction between leukemic and benign promyelocytes.