Sarcomatoid transitional cell carcinomas of the renal pelvis. An ultrastructural and immunohistochemical study.

Transitional cell carcinomas of the urinary tract may occasionally assume a partial or complete spindle cell pattern of growth, leading to the erroneous classification of some true carcinomas as sarcomas. We have recently observed two such tumors of the renal pelvis. In these cases, ultrastructural study showed that the spindle cells retained features of epithelial differentiation; this conclusion was further supported by positive results of several immunohistochemical stains, using biotinylated peanut agglutinin and soybean agglutinin, and a rabbit antiserum directed against keratin proteins. In addition, both tumors manifested immunoreactivity for blood-group antigens, using primary murine monoclonal antibodies. The results of these studies suggest that immunocytochemistry is a helpful diagnostic adjunct in the proper classification of sarcomatoid urothelial neoplasms.