Acute monoblastic leukemia with t(8;16): a distinct clinicopathologic entity; report of a case and review of the literature.

We report a case of acute monoblastic leukemia with t(8;16) in a 71-year-old man who had rapid rise of leukocyte counts from 20.3 x 10(9)/l to 62.7 x 10(9)/l in two weeks. The peripheral blood showed many granular promonocytes that led to the consideration of acute promyelocytic leukemia of the hypogranular variant. The bone marrow, however, revealed mainly monoblasts with erythrophagocytosis. Cytogenetic study finally confirmed the diagnosis of acute monoblastic leukemia with t(8;16). The patient died three days after admission. The demonstration of these two characteristic features of this subtype, granular promonocytes and erythrophagocytosis by monoblasts, separately, in the peripheral blood and bone marrow is unusual and misleading. This cytogenetic abnormality can be demonstrated only in M5 and M4 with characteristic clinical features of disseminated intravascular coagulation, extramedullary involvement, and poor prognosis. Although it is not a common disease, this specific subtype of acute myelogenous leukemia is consistently associated with a specific cytogenetic marker, thus it should be considered a distinct clinicopathologic entity.