Sarcomatoid renal cell carcinoma with scant carcinomatous components

A 30-year-old male underwent radical nephrectomy for a right renal tumor 15 cm in diameter. On microscopic examination of initial 17 sections, the tumor consisted of pleomorphic giant cells and spindle neoplastic cells. There was no carcinomatous component. Immunohistochemically, the neoplastic cells were negative for keratin and epithelial membrane antigen but positive for vimentin. The giant cells were also scatteringly, weakly positive for myoglobin. At that time a diagnosis of rhabdomyosarcoma of the kidney was made. However, further microscopic examination of another eight sections revealed small areas of clear cell-type renal cell carcinoma (RCC) which transited to sarcomatous components and led to a diagnosis of sarcomatoid RCC. The patient underwent three cycles of adjuvant chemotherapy. He has been free of the disease for 14 months after nephrectomy.