An unusual case of metastatic sarcomatoid renal cell carcinoma is presented. Fifteen months after nephrectomy for a typical clear cell carcinoma, a 63-year-old man presented with bilateral pleural effusions, cardiomegaly, and tamponade. A pericardial biopsy showed an anaplastic spindle cell tumor that was strongly keratin positive and showed desmosomes ultrastructurally. The patient died shortly thereafter, and the autopsy revealed massive tumor infiltration of the heart, pulmonary and adrenal metastases, and tumor nodules at the incision site of his nephrectomy. The differential diagnosis of sarcomatoid renal cell carcinoma is discussed.