Malignant interstitial (Leydig) cell tumour of the testis--a case report.

Interstitial (Leydig) cell tumour of the testis is an extremely uncommon tumour. We report one such tumour displaying histologic features of malignancy--large size capsular invasion and moderate nuclear pleomorphism in an adult male. The tumour also showed crystalloids of Reinke, confirming Leydig cell origin.