Rare presentation of carcinosarcoma arising in bladder diverticulum

An 87-year-old man presented with hematuria and dysuria. An endoscopic exam ination revealed a bladder mucosa which was almost entirely occupied by div erticula. On the left lateral wall of the bladder there was a huge divertic ulum which contained a 12 cm mass extending beyond the bladder wall in the extraperitoneal tissues. Upon histological examination the mass proved to b e a carcinosarcoma which was composed by a squamous carcinoma and a sarcoma resembling a malignant fibrous histiocytoma. The two components, i.e. carc inomatous and sarcomatous, were separated by a sharp collision border and n o intermingling was ever noted. The epithelial component showed immunoreact ivity for cytokeratin and EMA, while the mesenchymal component was diffusel y reactive for vimentin, alpha-l-antitrypsin and lysozime. Both components were reactive for galectin-3, whereas S100, desmin and smooth muscle actin were negative. This is the fourth reported case of carcinosarcoma originati ng in a bladder diverticulum.