A Becker nevus (Becker melanosis) is an acquired, benign, melanocytic epidermal proliferation of adolescence. It typically presents as a large, hyperpigmented patch with increased hair growth on the upper trunk in men. This lesion is not uncommon and is found in all ethnicities. Lesions are usually present before puberty but often have increased coarse hair growth and a slightly raised texture during adolescence due to androgen stimulation. Rarely, there can be associated hypoplasia of the underlying tissues (eg, breast hypoplasia, pectoralis hypoplasia, or limb hypoplasia). Most Becker nevi have no associated abnormalities.

Treatment is only required in rare cases for severe cosmetic or psychosocial reasons. Other rare associated findings include acne, acanthosis nigricans, spina bifida, scoliosis, pectus carinatum, accessory scrotum, lipoatrophy, and congenital adrenal hyperplasia. A few cases of melanoma in association with a Becker nevus have been reported.