Smooth-muscle hamartoma. Possible congenital Becker's nevus.
D003937:Diagnosis, Differential; D005260:Female; D006222:Hamartoma / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D007231:Infant, Newborn; D008548:Melanosis / Q000175:diagnosis; D009130:Muscle, Smooth; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000473:pathology