Congenital smooth muscle hamartoma masquerading as congenital pigmented nevus.

Smooth muscle hamartomas are rare benign tumors of the skin, characterized by proliferation of large interlacing bundles of nonstriated muscle within the reticular dermis. The lesions may masquerade as one of several clinical entities. In this report, we describe two patients with congenital smooth muscle hamartomas masquerading as congenital pigmented nevi. Review of the literature indicates that these cases represent the ninth and tenth reported cases of congenital smooth muscle hamartoma. Our second case represents the largest lesion reported to date.