testicular Leydig cell tumor
A sex cord-stromal tumor that arises from the testis and is characterized by the presence of cells that resemble the successive stages of development of Leydig cells. It usually presents as a painless testicular mass. Gynecomastia is present in approximately thirty percent of the cases. Libido may be decreased. In children, precocious puberty may be present. A minority of cases exhibit malignant characteristics.