[Epidermoid cyst of the testis difficult to make a preoperative diagnosis on the echoic examination: a case report].

A case of epidermoid cyst of the testis is presented. The patient was a 64-year-old man who complained of a painless mass in the left scrotum. Physical examination revealed a hen-egg sized enlargement of the left scrotal contents. The ultrasonographic appearance did not show a hyperechoic partition, which is called echogenic rim, a characteristic of this tumor on the echoic examination, and was homogeneous, almost similar to that of a normal testis. Because malignant testicular tumors could not be excluded preoperatively, excisional biopsy of the left testis was performed first. Histological diagnosis was an epidermoid cyst of the testis. As the left testis was almost completely occupied by the tumor and no normal testicular tissue was recognized, we performed orchiectomy additionally. Epidermoid cyst of the testis is a rare benign tumor that accounts for about 1 percent of all testicular tumors. It clinically resembles malignant testicular tumors, and orchiectomy is often performed for treatment. About 154 cases of testicular epidermoid cyst have been reported in the Japanese literature and are reviewed briefly here.