Organoid nevus.

The organoid nevus is a malformation of most of the normal tissue components in a strictly localized, smaller or larger area of skin, most commonly the scalp. It undergoes more or less predictable developmental changes in puberty and then remains stable, but is subject to secondary development of benign or semimalignant adnexal tumors in a significant percentage of cases. It may present clinically and histologically in a variety of forms, the most common ones being nevus sebaceus and nevus verrucosus. It may be associated with neurologic and skeletal abnormalities in the organoid nevus syndrome (Schimmelpenning-Feuerstein-Mims). Total excision before adolescence is the treatment of choice.