Extramedullary hematopoiesis in the endometrium.

Extramedullary hematopoiesis (EMH) in the endometrium is an extremely rare occurrence. Four of the eight previously reported cases were related to an underlying hematological disorder, although the remainder had no such relationship. We describe a case of endometrial EMH associated with retained products of conception after termination of pregnancy. Routinely and immunohistochemically stained slides revealed several collections of normoblasts and granulocytic precursors in the endometrium with synchronous chronic endometritis. Retained chorionic villi were also identified. The patient had no known history of a hematological disorder or systemic disease and no such abnormality was detected after detailed hematological work-up. Local effects of growth factors on circulating stem cells may play a pathogenetic role in this process, although an association with recent pregnancy in this case suggests that implantation of fetal hematopoietic elements from the fetus or yolk sac may be more likely.