Metastatic Leydig cell tumor with sarcomatoid differentiation

Leydig cell tumors of the testis are uncommon. Only about 10% of cases have a malignant course. It has been stated that the only definite criterion fo r malignancy is presence of metastasis. We present a 47-year-old patient wi th metastatic Leydig cell tumor 17 years after initial diagnosis, to our kn owledge the longest reported interval between diagnosis and the development of metastasis. The primary tumor did not exhibit convincing features of ma lignancy. The initial metastasis in the right perirenal fat tissue showed a biphasic tumor with sarcomatoid differentiation not described previously i n a metastatic Leydig cell tumor.