Rare presentation of carcinosarcoma arising in bladder diverticulum.

An 87-year-old man presented with hematuria and dysuria. An endoscopic examination revealed a bladder mucosa which was almost entirely occupied by diverticula. On the left lateral wall of the bladder there was a huge diverticulum which contained a 12 cm mass extending beyond the bladder wall in the extraperitoneal tissues. Upon histological examination the mass proved to be a carcinosarcoma which was composed by a squamous carcinoma and a sarcoma resembling a malignant fibrous histiocytoma. The two components, i.e. carcinomatous and sarcomatous, were separated by a sharp collision border and no intermingling was ever noted. The epithelial component showed immunoreactivity for cytokeratin and EMA, while the mesenchymal component was diffusely reactive for vimentin, alpha-1-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 originating in a bladder diverticulum.