Sarcomatoid carcinoma of the renal pelvis with giant cell tumor-like features: case report with immunohistochemical findings.

Sarcomatoid transitional cell carcinoma is a rare entity, in which a malignant, overtly epithelial component coexists with areas having a sarcoma-like appearance. Histological distinction of sarcomatoid carcinomas from carcinosarcomas is often difficult and immunohistochemistry is a helpful diagnostic adjunct in the correct diagnosis. In the present report, we describe an uncommon case of sarcomatoid transitional cell carcinoma of the renal pelvis, associated with giant cell tumor-like features. Immunoperoxidase staining for cytokeratin was positive in spindle cell component, indicating an epithelial origin. The carcinomatous component showed a diffuse membranous reactivity for E-cadherin, whereas the reactivity was sporadic and weaker in the sarcomatoid component, suggesting that the decrease of E-cadherin expression might be associated with the acquisition of sarcomatous morphology. Osteoclast-like multinucleated giant cells were positive for CD68 and negative for p53 oncoprotein, suggesting that they represent a non-neoplastic component that is reactively induced in the tumor stroma.