"Microgranular" acute promyelocytic leukemia: a distinct clinical, ultrastructural, and cytogenetic entity

Abstract

Three patients with acute leukemia, disseminated intravascular coagulation, and a specific acquired chromosome abnormality [t (15;17)] were found by transmission electron microscopy to have the typical distribution of granules seen in promyelocytes. However, the average granule sizes were 120, 170, and 180 nm, respectively, for the three patients, significantly less than the 250-nm resolution of light microscopy. We regard the leukemia in these three patients as comprising a distinct clinical, ultrastructural, and cytogenetic entity that we have chosen to call "microgranular" acute promyelocytic leukemia.