Schwannoma of the kidney.

Schwannomas of the kidney are rare, with only a few reported cases. We report three additional cases with immunohistochemical analysis. All three tumors were from females (aged 27, 35, and 59 years) and ranged from 4.8 to 8 cm in diameter. All of the patients underwent nephrectomy. The tumors were totally or partially encapsulated; two were in the hilum and one was centered in the renal cortex. All tumors were diffusely positive for S100 protein. Two were positive for neuron-specific enolase. Immunostaining for neurofilament, HMB45, microphthalmia transcription factor, smooth muscle actin, CD34, cytokeratin AE1/3, cytokeratin 7, and CD10 were negative. Follow-up data were available for two patients; neither had tumor recurrence or metastasis. In conclusion, renal schwannoma is rare, usually arises centrally, impinging on the hilum or the pelvis, and is cured by resection. Sarcomatoid carcinoma and other spindle cell tumors should be considered in the differential diagnosis.