Morphology and cytochemistry of "microgranular" acute promyelocytic leukemia (FAB M3m)

Three cases of a newly recognized "microgranular" variant of acute promyelocytic leukemia (FAB M3) are described. This poor-prognosis variant is easily confused with myelomonocytic (M4) or monocytic (M5) leukemia, but is associated with disseminated intravascular coagulation as is "hypergranular" M3. Such patients may be inappropriately treated unless the promyelocytic nature of the leukemia is recognized.