Congenital smooth muscle hamartoma.

Congenital smooth muscle hamartoma is usually apparent at birth. The lesion may be skin-colored or hyperpigmented and may appear hypertrichotic. Histologically characterized by proliferation of smooth muscle bundles in the dermis, this congenital lesion is not associated with underlying developmental abnormalities or malignant potential, but it may be mistaken for the types of lesions that accompany congenital anomalies or carry a risk of malignancy.