Inflammatory pseudotumor of the urinary bladder and sigmoid colon.

We report an unusual case of an inflammatory pseudotumor of the bladder. A biopsy specimen prior to surgical treatment suggested leiomyosarcoma, and computerized tomography and magnetic resonance imaging strongly suggested bladder tumor with sigmoid colon invasion. Accordingly, radical surgical treatment consisting of total cystectomy, anterior resection of the sigmoid colon, and ileal conduit was performed. After operation, however, histological examination revealed an inflammatory pseudotumor of bladder and sigmoid colon. These findings were confirmed by immunohistochemical staining for smooth muscle specific actin, desmin, S-100, and vimentin. Histological examination revealed a diverticulum of the sigmoid colon in the middle of the pseudotumor, and this diverticulum may have ruptured to cause the inflammatory pseudotumor of bladder and sigmoid colon.