Myeloid metaplasia masquerading as a urethral caruncle.

A 64-year-old woman presented with a painless bleeding mass of the urethral meatus that was diagnosed as a caruncle and removed surgically. Histological examination revealed a cellular and vascular polypoid lesion that contained megakaryocytes, as well as groups of hematopoietic stem cells, and maturing cells of the erythroid and granulocytic series. The diagnosis of myeloid metaplasia was confirmed by marker studies with immunoperoxidase techniques. The patient had a long history of bleeding and clotting problems owing to a myeloproliferative disorder with thrombocytosis and gradual development of myelofibrosis. No other foci of extramedullary hematopoiesis were apparent. The patient was free of urinary symptoms 22 months postoperatively.