Extramedullary Hematopoiesis of the Urinary Bladder Associated With Metastatic Prostatic Adenocarcinoma: A Case Report.

Extramedullary hematopoiesis (EMH) is the production of hematopoietic cells outside the bone marrow, which most commonly occurs in the liver, spleen, and lymph nodes. EMH involving the urinary bladder is exceptionally rare, with only a few cases reported. We present the first known case of bladder EMH secondary to bone marrow metastasis from prostatic adenocarcinoma. The patient presented with gross hematuria; cystoscopy revealed multiple bladder masses. Histopathological examination demonstrated erythroid and myeloid precursors, along with scattered megakaryocytes, confirmed by immunohistochemistry. Bladder EMH should be considered in the differential diagnosis of patients with solid tumors presenting with hematuria. Hemorrhagic cystitis can mimic this entity and lead to misdiagnosis. The awareness of this rare manifestation is essential for accurate diagnosis and appropriate management.