Necrotizing palisading granuloma of the bladder in an otherwise healthy young man.

We describe a case of a vesical mass in a young patient, histologically characterized by an intramural lesion composed of spindle and epithelioid histiocytes arranged in a palisaded pattern, with central necrosis similar to a rheumatoid nodule. There was no clinical history of autoimmunity or previous bladder procedures, infections, or trauma. However, the smooth muscle actin and desmin positivities seen in residual ghost cells within necrotic areas argued against a granulomatous process. Reactive processes, such as myofibroblastic proliferations, can overlap neoplastic disorders, including true smooth muscle tumors. We did not observe atypia in the viable cells and mitotic figures. These features did not support a diagnosis of malignancy. The fascicular pattern, spindle cell morphology, lack of marked cytologic atypia, and smooth muscle actin and desmin reactivities, with a lack of other lineage marker expression, all supported a diagnosis of an infarcted leiomyoma. The intramural location in the bladder also favored the diagnosis.