Sarcomatoid carcinoma of the urinary bladder: a clinicopathologic and immunohistochemical analysis of 14 patients.

Sarcomatoid carcinoma of the urinary bladder is a rare entity, in which both the histogenesis and biological behavior remain controversial. We herein describe the clinicopathologic and immunohistochemical profiles of sarcomatoid carcinomas and discuss the significance of cell adhesion molecules in the development of this peculiar neoplasm. The authors examined formalin-fixed and paraffin-embedded tissue samples from 14 patients with sarcomatoid carcinoma of the urinary bladder. An immunohistochemical analysis was performed by using antibodies against epithelial and mesenchymal antigens as well as adhesion molecules. Most patients suffered from an advanced stage of the tumor, extending to the muscular layer (7 cases) or to the perivesical tissues (5 cases). Microscopically, all 14 tumors were composed predominantly of a carcomatoid component and an obviously carcinomatous component. The sarcomatoid component was composed of a mixture of spindle cells, round cells, and pleomorphic giant cells. The carcinomatous components consisted of papillary or nonpapillary high-grade transitional cell carcinoma (TCC). The zones of gradual transition between the carcinomatous and the sarcomatous elements were focally apparent in each tumor. The findings of an immunohistochemical examination indicated that both carcinomatous and sarcomatoid components expressed epithelial antigens (pankeratin or EMA), even though the staining pattern varied from case to case. As for cell adhesion molecules, the carcinomatous components were positive for E-cadherin (8 of 12), CD44s (8 of 12), and CD44v6 (6 of 12). Although the sarcomatoid components were also positive for E-cadherin (5 of 12), CD44s (4 of 12), and CD44v6 (3 of 12), these rates were lower than those in the carcinomatous components. Six patients died of their disease between 5 and 36 months after the diagnosis was made. The recognition of sarcomatoid carcinomas has important therapeutic and prognostic implications. It seems appropriate to treat these neoplasms in the same manner as conventional high-grade TCCs with similar degrees of invasion. We consider that sarcomatoid carcinomas should be regarded as a high-grade carcinoma that shows a prominent pseudosarcomatous dedifferentiation. The sarcomatoid component of sarcomatoid carcinomas may result from either anaplastic changes or dedifferentiation related to the process of losing cell adhesion molecules.