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Beckers Melanosis
Becker's melanosis, also called Becker's pigmented hairy nevus, occurs most commonly as a large, unilateral patch showing hyperpigmentation and hypertrichosis on the shoulder, back, or chest of a male adult . Usually, the patch is sharply but irregularly demarcated. Occasionally, however, the lesion presents as coalescing macules instead of a solitary patch. The lesion commonly appears during the second decade of life. In some instances, Becker's melanosis affects areas other than the shoulder and chest. In addition, it may be multiple and bilateral and may occasionally be found in women.
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In one report, nine cases of melanoma in association with Becker's nevus were described . Five of these were on the same body site as the nevus. It remains to be determined whether these reports represent a greater incidence than chance would suggest.
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The hairiness always appears after the pigmentation, and, quite frequently, no hypertrichosis is seen. It is therefore possible that cases described as progressive cribriform and zosteriform hyperpigmentation represent a variant of Becker's melanosis without hypertrichosis .
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Of interest is the association of a pilar smooth muscle hamartoma with Becker's melanosis. In such cases, the area of Becker's melanosis may show slight perifollicular papular elevations or slight induration .
Histopathology
. The epidermis shows slight acanthosis and regular elongation of the rete ridges. There is hyperpigmentation of the basal layer, and melanophages are seen in the upper dermis. The number of melanocytes is increased within the basal cell layer. This increase is particularly evident when melanocytes are stained for dopa-oxidase activity in both involved and uninvolved skin nearby . The pilar structures appear normal or increased in number.
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An increase in smooth muscle fibers exists in nearly all cases, although it may be slight . In cases with an associated smooth muscle hamartoma, irregularly arranged, thick bundles of smooth muscle are present in the dermis . The term Becker nevus syndrome has been proposed for a phenotype characterized by the presence of a particular type of organoid epithelial nevus showing hyperpigmentation, increased hairiness, hamartomatous augmentation of smooth muscle fibers (smooth muscle hamartoma), and other developmental defects such as ipsilateral hypoplasia of breast and skeletal anomalies including scoliosis, spina bifida occulta, and ipsilateral hypoplasia of a limb .
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The few melanomas that have been described in association with Becker's nevus have been of the superficial spreading type, originating in the epidermis .
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