Chromophobe renal cell carcinoma with osteosarcoma differentiation: case report and literature review.

Chromophobe renal cell carcinoma is a distinct subtype of renal cell carcinoma that is well known for its relatively good prognosis. When it presents with sarcomatoid differentiation, necrosis of the sarcomatoid area or angiolymphatic invasion, it becomes a highly aggressive neoplasm. The presence of osteosarcoma-like elements in sarcomatoid chromophobe renal cell carcinoma is very rare as only 5 cases have been reported previously. We present a 6th case of sarcomatoid chromophobe renal cell carcinoma, which had an osteosarcoma differentiation component. However, the correlation between the presence of heterologous elements and prognosis is unknown because of the rarity of this phenomenon.