Cutaneous metastasis of renal cell carcinoma: a report of two cases.

Cutaneous metastasis of renal cell carcinoma (RCC) is very rare. The author herein report two cases of RCC with cutaneous metastasis. Case 1: is a 75-year-old man with right lumbago. Imaging modalities including CT and MRI revealed a right renal tumor. Nephrectomy was performed. Pathological diagnosis of the renal tumor was RCC of clear cell type (Fuhrman's grade II). He denied follow-up. Nine years later, he (at the age of 84 years), a neck skin tumor emerged. Clinical diagnosis was hemangioma. Imaging modalities including CT and MRI showed several tumors in both lungs. The resection of the neck tumor was performed. The tumor was composed of clear cell type arranged in a trabecular pattern. Immunohistochemically, the tumor cells were positive for pancytokeratins, cytokeratin 18, CD10, Ki-67 (labeling=13%), but negative for CD34, factor-VIII-related antigen, CEA, EMA, melanosome (HMB45), S100 protein, p53, and HepPar-1. Metastatic RCC was diagnosed. Despite interferon therapy, he died of 6 months after the second admission. Case 2 is a 66-year-old man with gross hematuria. Imaging modalities revealed left renal tumor. A nephrectomy was performed. The pathological diagnosis was RCC of clear cell type (grade II). The tumor was invasive into the renal pelvis. He was treated by chemoradiation, but metastases of lungs, skin (thigh), and lib emerged, and died of cachexia 9 months after the admission. Necropsy of the skin tumor was performed. The skin tumor was composed of clear cells arranged in a trabecular pattern. Immunohistochemically, the tumor cells were positive for pancytokeratins (AE1/3, CAM5.2), CD10, p53, and Ki-67 (labeling=20%), but negative for CD34, factor-VIII-related antigen, CEA, melanosome (HMB45), S100 protein, and HepPar-1. A diagnosis of RCC (grade II) was diagnosed.