[Solitary genital leiomyoma of the tunica dartos: a case report and review of the literature in Japan].

We report a case of solitary genital leiomyoma arising from the tunica dartos of the scrotum. A 43-year-old man complained of a slightly tender left scrotal mass that had enlarged over approximately 17 years. On physical examination, the tumor was pedunculate and attached to the lower pole of the left scrotum. The tumor was clearly separate from scrotal contents such as the testis, epididymis, and spermatic cord. Ultrasonography showed the tumor to be 20.0 X 23.5 mm in diameter. Other laboratory examination findings were normal. Under local anesthesia, the tumor was resected at its base with overlying skin. On histopathological examination, the tumor consisted of interlacing bundles of smooth muscle cells, which were positive for vimentin, desmin, and a-actin. The tumor was diagnosed as leiomyoma arising from the scrotal tunica dartos. As solitary genital leiomyoma of the tunica dartos is rare, we have presented this case history and reviewed 23 cases that occurred in Japan.