Case: A 32 year-old Hispanic male is concerned about a dark patch on his left shoulder that he says first appeared as a young adolescent and it has stayed the same in size, shape and color since that time (See image above). He is bothered by the fact that it grows hair in the patch and shaves it on occasion to be similar with the rest of his skin (shaven in the photo). He has no history of significant sun exposure, sunburns and no personal or family history of skin cancer.
Discussion: Becker’s nevus is a well-demarcated tan-to-brown patch with irregular borders that most commonly occurs over the shoulder, back or upper chest. Hypertrichosis (growth of hair in excess amount) is classically seen in these lesions and the hair may become coarser and darker over time.
It occurs in all races and is more common in males. These lesions tend to blossom during puberty because they have hormone receptors that respond to the elevated hormones during puberty. The pigmentation often darkens during the pubertal years as a result of increased hormones and the patch may grow for one to two years, eventually stabilizing to its final size.
On histologic exam, the epidermis demonstrates mild thickening (acanthosis) and the dermis reveals a slight increase in dermal smooth muscle with an increased number of follicular units (represented clinically by hypertrichosis). The hyper-pigmentation is related to increased melanin content in the keratinocytes as the number of melanocytes is usually normal or only slightly increased.
Becker’s nevus is a benign process but in rare cases it has been associated with soft tissue and bony abnormalities which include, hypoplasia of underlying structures, ipsilateral limb shortening and scoliosis. With its characteristic appearance, a biopsy is generally not necessary but referral to a dermatologist is prudent to be sure that one is not missing a diagnosis. The lesion should be closely monitored over time to be sure that no changes occur.
Intervention is only for cosmetic purposes and one should be realistic in terms of the improvement that can be achieved. The Q-switched ruby or Nd;YAG lasers can achieve modest improvement in the hyper-pigmentation component of the lesion. Electrolysis or waxing for hair removal and camouflage make-up are other options.
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