Acquired smooth-muscle hamartoma.

A 52-year-old woman presented with an occasionally pruritic, hyperpigmented and hypertrichotic, indurated plaque on the left upper arm that initially developed during childhood. Histopathologic examination showed changes that were consistent with a smooth-muscle hamartoma. Cutaneous smooth-muscle hamartomas are uncommon benign neoplasms. Most lesions are congenital, but there have been a few reports of acquired lesions. These lesions have been described as part of a spectrum of neoplasms that include Becker nevi since they share many clinical and histopathologic features.