A group of rare tumors of testis comprising neoplasms of pure sex cord or pure stromal type, or neoplasms with admixtures of both components in various proportions and degree of differentiation. The tumors usually present as a painless testicular mass, although some may be associated with endocrine manifestations such as precocious puberty, gynecomastia, or erectile dysfunction. Malignant behavior is seen only in a small percentage of these tumors. [from
ORDO]