Smooth-muscle hamartoma of the tunica dartos of the scrotum: report of a case.

Hamartomatous proliferations of genital smooth muscle are uncommon and may be easily overlooked if the normal microscopic appearance of the scrotal dartos is unfamiliar to the pathologist. We describe a hamartomatous proliferation of the scrotum in a 60-year-old patient in which incomplete knowledge of the regional histology caused initial problems in diagnosis. On histologic examination, the lesion consisted of an expansile, unencapsulated, relatively circumscribed proliferation of smooth muscle accompanied by muscular arterioles and prominent nerve branches embedded in a densely collagenized stroma. These features are dissimilar both clinically and histologically from all previous reported lesions at this site. We highlight the histologic differences between our case and genital leiomyomas, and the spectrum of hamartomatous smooth-muscle proliferations associated with a Becker nevus, and congenital and acquired smooth muscle hamartomas.