A case of acquired smooth muscle hamartoma of the scrotum.

We report a case of acquired smooth muscle hamartoma (ASMH) of tunica dartos, believed to be only the fifth so far reported. A 24-year-old man had a 6-month history of an asymptomatic tight and thickened scrotum. The skin was difficult to pinch. A biopsy specimen from the skin showed increased and proliferated smooth-muscle bundles composed of well-differentiated and uniform spindle cells that showed typical features of acquired smooth muscle hamartoma. Interestingly, dilatations of the lymph vessels were noted in the upper dermis above the proliferated smooth muscles. It has been reported recently that long-standing severe lymphoedema may cause histological features mimicking ASMH. As the present case was not preceded by oedema of the scrotum, we consider this case to be true ASMH.