Extramedullary hematopoiesis in the endometrium. Report of four cases and review of the literature.

Extramedullary hematopoiesis is extremely rare in the absence of any hematologic disorder or systemic disease, and there have been no reports of this condition in the endometrium. The authors describe the cases of four patients who complained of irregular uterine bleeding, lower abdominal pain, or both. Microscopic examination of the curetted endometria showed chronic inflammation in two patients, chronic inflammation and leiomyomas in one patient, and a well-differentiated adenosquamous adenocarcinoma with adenomyosis and leiomyomas in one patient. Light-microscopic examination of curetted sections from all four patients revealed isolated foci of extramedullary hematopoiesis composed of one or more lineages of blood cell precursors. Sufficient tissue was available from two patients to confirm hematopoietic differentiation through immunohistologic analysis, using antibodies to von Willebrand factor, ABH blood group antigens, CD34, and CD15.