Sarcomatoid chromophobe renal cell carcinoma with heterologous sarcomatoid elements. A case report and review of the literature.

Chromophobe renal cell carcinoma (CRCC) is a distinct subtype of renal cell carcinoma (RCC) that is well known for its relatively good prognosis. Sarcomatoid transformation in this tumor, although rare, has been well documented in the literature and, as in other types of RCC, carries an ominous prognosis for the patient. The finding of heterologous elements in the sarcomatoid component of CRCC is an extraordinary event, which has been reported in only 2 previous cases. Here, we present the third such case, occurring in the left kidney of a previously healthy 63-year-old woman. The nephrectomy specimen showed CRCC with extensive sarcomatoid changes displaying heterologous elements in the form of chondrosarcomatous and osteosarcomatous differentiation. As in other sarcomatoid RCCs, this tumor behaves aggressively, with frequent distant metastases. It is important to recognize the sarcomatoid component in these tumors because of its consequential adverse prognosis for the patient.