Becker's Nevus

Becker's nevus, also known as pigmented hairy epidermal nevus, mostly occurs after birth, is more common in males, and often appears on the shoulders. Clinically, it presents as a slightly elevated pigmented patch with increased hair on the surface. This condition can slowly enlarge over 1-2 years and then remain stable. It is a benign lesion, but some patients may have congenital developmental abnormalities.

1. Cause and Pathogenesis

The cause of Becker's nevus is not clear. Some studies suggest it is related to the overexpression of androgen receptors in dermal fibroblasts. It is generally considered to be acquired, but there are reports of congenital cases and familial inheritance.

2. Clinical Manifestations

Becker's nevus often occurs during childhood and adolescence, with a male-to-female ratio of 5:1. It usually appears after intense sun exposure. The lesions commonly appear on the chest, back, and shoulders, and less frequently on the face and neck. Shoulder lesions are often unilateral. The lesions present as sudden pigmented patches that darken with age and sun exposure. The patches enlarge and new pigmented spots may appear. The patches are irregular, light brown to dark brown with clear borders. The lesions can be slightly raised, and the central skin may be slightly thickened, rough, and wrinkled, with increased, thicker, and darker hair. There are generally no subjective symptoms, but some patients may experience itching. The condition can enlarge over 1-2 years and then stabilize. Some patients may have congenital abnormalities, such as unilateral breast hypoplasia, ipsilateral pectoralis muscle hypoplasia, ipsilateral limb shortening, elongated ipsilateral foot, spina bifida, pectus carinatum, localized subcutaneous fat atrophy, congenital adrenal hyperplasia, and supernumerary nipples, also known as Becker's nevus syndrome. Becker's nevus can also be associated with other conditions such as leiomyoma, lichen planus, and melanocytic nevus.

3. Pathological Characteristics

Becker's nevus does not contain nevus cells. The epidermis shows hyperkeratosis, acanthosis, papillomatous hyperplasia, and regular elongation of the rete ridges. There is an increase in melanin within keratinocytes. The basal and spinous layers show a significant increase in melanin, but the number of melanocytes is normal. Hair follicles and sebaceous glands are hyperplastic. Melanophages can be seen in the dermis, and some areas may show thickened, irregularly arranged smooth muscle bundles.

4. Diagnosis and Differential Diagnosis

Becker's nevus should be considered in male patients with unilateral pigmented patches on the shoulder and back that appear around puberty and have increased hair on the surface. Clinically, it should be differentiated from nevus of Ito and congenital melanocytic nevus.

5. Treatment

Becker's nevus is generally considered benign and does not require treatment. For cosmetic reasons, Q-switched laser and hair removal laser treatments can be used. Traditional treatments such as cryotherapy and ablative laser treatments are not effective and may cause scarring, and are thus no longer used. Laser treatments and precautions are similar to those for café-au-lait spots, but the efficacy is uncertain and only partially effective, usually only improving the appearance of the lesions to varying degrees. Patients should be fully informed before treatment to avoid unrealistic expectations.

(i) Q-Switched Laser Treatment

Q-switched Alexandrite laser (wavelength 755nm), Q-switched Ruby laser (wavelength 694nm), and Q-switched Frequency-Doubled Nd

laser (wavelength 532nm, 1064nm) can effectively reduce the pigmentation of Becker's nevus. Multiple treatments are generally required, with intervals of 5-6 months. However, some patients may not respond or may experience recurrence.

(ii) Long-Pulsed Hair Removal Laser Treatment

Long-pulsed Alexandrite laser (wavelength 755nm), pulse width 3ms, is effective in damaging hair follicles and the longer the pulse width, the more the pigmented structures can be heated. Since melanocytes in the deep hair follicles are effectively destroyed, the effect of laser treatment on pigment lesions can be sustained longer. Treatment spots of 15mm with an energy density of 25J/cm², or 18mm spots with an energy density of 20J/cm², with cooling spray turned off, can be treated every 2-3 months. On average, 2 treatments can significantly reduce hair and improve pigmentation in Becker's nevus.

(iii) Other Treatments

Semiconductor laser (wavelength 810nm), long-pulsed Nd

laser (wavelength 1064nm), intense pulsed light hair removal, and erbium laser treatments are also effective for Becker's nevus, but have more significant side effects such as persistent erythema, scarring, and pigment changes. Fractional lasers have also been used to treat Becker's nevus, but they are usually not effective for the hypertrichosis associated with Becker's nevus. For cases with both pigmentation and hypertrichosis, long-pulsed pigmented lasers are the best choice.

Source: Becker's Nevus