Sarcomatoid renal cell carcinoma. An immunohistochemical and ultrastructural study.

A case of sarcomatoid renal cell carcinoma is reported with light, immunohistochemical and electron microscopic findings. The tumour consisted of typical clear cells of renal cell carcinoma and spindle cells compatible with malignant fibrous histiocytoma (MFH). Although an epithelial membrane antigen was demonstrated in the clear cells, this was not detected in the MFH-like spindle cells. In contrast, the spindle cells expressed vimentin that was not identified in the clear cells. Electron microscopy reveal epithelial features in the spindle cells. Comparisons were made with previous sarcomatoid renal cell carcinoma in the literature. Thus, ultrastructural study was vital in diagnosis of sarcomatoid renal cell carcinoma.