Renal cell carcinoma with rhabdoid features. Divergent differentiation of conventional (clear cell) carcinoma.

A rare case of renal cell carcinoma (RCC) with rhabdoid features in an adult man is presented. This tumor with rhabdoid features, also known as composite neoplasm, represents a pattern of progression emerging from specific histologic RCC types. RCC with rhabdoid features is a highly aggressive neoplasm and its malignant behavior may be due to the high-cell proliferation activity of the rhabdoid areas. Rhabdoid features in RCC may represent a final pathway of differentiation in clonal progression to a high-grade, aggressive biologic state.