Extramedullary hematopoiesis in the uterine isthmus: a case report and review of the literature.

Extramedullary hematopoiesis (EH) is the ectopic production of myeloid, erythroid and megakaryocytic elements. In postfetal life it usually occurs in conditions with hyperactive, depleted or infiltrated marrow; it is extremely rare in the genital tract. We report a case of EH in the uterine isthmus (UI) which was found incidentally in a 40-year-old patient who presented with a right ovarian cyst and a history of a right modified radical mastectomy for infiltrating invasive lobular carcinoma one year earlier. The patient underwent total abdominal hysterectomy with bilateral salpingo-oophorectomy. Microscopic examination of UI revealed foci of hematopoiesis, consisting of white blood cell precursors confirmed by positive chloroacetate-esterase staining. Bone marrow biospy showed diffuse infiltration secondary to breast cancer. Further work-up, including a bone scan, showed multiple metastases suggesting that the high degree of bone marrow infiltration by neoplasmatic cells had stimulated the EH. In conclusion, the unusual finding of EH in UI heralded widespread infiltration of bone marrow.