MYXOID AND SCLEROSING SARCOMATOID TRANSITIONAL CELL CARCINOMA OF THE URINARY BLADDER : A CLINICOPATHOLOGIC AND IMMUNOHISTOCHEMICAL STUDY OF 25 CASES

: We report 25 sarcomatoid carcinomas of the urinary bladder with a prominent myxoid and/or sclerotic appearance. The average age of the patients was 72 years (range, 50-92 yr); 14 were men, and 11 were women. The cystoscopic appearance varied from a large polypoid mass to an intramural mass with bladder wall thickening, often with necrosis and ulceration. The tumors ranged from 3 to 10 cm and were typically rubbery or gelatinous with a brown, pink, or gray color. Microscopy revealed tapering spindle cells with a variable admixture of cohesive non-spindled cells. Twenty-two cases had an invasive overtly epithelial carcinomatous component, and in situ transitional carcinoma was present in 12 cases. All of the cases had areas with myxoid change, ranging from extensive to focal, separating the spindle cells. Fourteen cases had areas of sclerosis. In all the cases, the spindle cells were atypical, at least focally, with hyperchromatic pleomorphic nuclei, prominent nucleoli, and coarse chromatin. Mitotic activity was prominent in the majority of cases, and abnormal mitotic figures were frequent. In eight cases, the myxoid histologic pattern was very reminiscent of an inflammatory pseudotumor, a diagnosis frequently entertained and erroneously made in one case; many of the spindle cells in three of these cases were mildly atypical, with minimal mitotic activity. The spindle cells were immunoreactive for cytokeratin (12 of 19), vimentin (16 of 17), carcinoembryonic antigen (3 of 15) and muscle-specific actin (4 of 16), and nonreactive for epithelial membrane antigen, desmin, S-100, KP1, CD34, and Leu-M1. The epithelioid carcinomatous areas were highlighted by the cytokeratin immunostain. These features and the conventional light microscopic features indicative of a diagnosis of carcinoma distinguish this tumor from reactive of neoplastic mesenchymal lesions.