Becker's nevus: an androgen-mediated hyperplasia with increased androgen receptors.

Becker's nevus is an uncommon, unilateral, hyperpigmented, hairy cutaneous hamartoma which usually begins in adolescence. Its clinical features and its occurrence mainly in male individuals suggest that androgen stimulation may play a role in its pathogenesis. Androgen receptor assays were performed in a 16-year-old patient with a Becker's nevus. The patient coincidentally had acanthosis nigricans. Lesional tissue showed an androgen receptor level of 634.1 fm/mg protein. A specimen from the contralateral left pectoral area showed no dectectable androgen receptor activity (less than 2.0 fm/mg protein). These results suggest that exquisite androgen sensitivity and stimulation may explain the clinical manifestations of Becker's nevus.