BECKER'S NEVUS

 

 (BECKER

 

HAMARTOMA,

 

 BECKER MELANOSIS)

 

This acquired hyperpigmented epidermal nevus was first described by Becker in 1949  It preferentially occurs in the scapular region, although it has been described in any area of the body, and classically after an intense sun exposure. The lesion is androgen-dependent and becomes more prominent in adolescence, especially in the male population in which hypertrichosis is often associated. Associated anomalies, such as ipsilateral breast hypoplasia, musculoskeletal abnormalities (scoliosis, ipsilateral limb hypoplasia, etc.), maxillofacial abnormalities, and additional cutaneous hypoplasias, occur in the rare Becker's nevus syndrome. Microscopic examination demonstrates normal numbers of melanocytes, but increased levels of melanin in the basal epidermal layer (epidermal melanotic hypermelanosis). The epidermis is acanthotic with variable hyperkeratosis and elongation of the rete ridges. In the dermis, the number of arrector pili muscles is increased, making it difficult to differentiate from the related smooth muscle hamartoma.

Becker's nevus is suggested to follow a paradominant inheritance pattern, which means it (almost) always occurs sporadically. The rare familial cases that have been described (especially in Becker's nevus syndrome) can be explained by a somatic mutation during embryogenesis, resulting in loss of heterozygosity and formation of a mutant cell population. Moreover, a chromosomal mosaicism has been detected in fibroblasts derived from a Becker's nevus