Dermatology

Becker's nevus (Becker's melanosis, Becker's pigmentary hamartoma, nevoid melanosis, pigmented hairy epidermal nevus)

Are You Confident of the Diagnosis?

Becker’s nevus is a cutaneous hamartoma composed of hair follicles and arrector pili muscles and is not a true nevomelanocytic lesion. Hence the term, Becker’s nevus, is actually a misnomer. The diagnosis of Becker’s nevus is typically made clinically, although a biopsy may be necessary in some cases to differentiate the lesion from congenital melanocytic nevus.

What you should be alert for in the history

Becker’s nevus usually presents as a unilateral, hyperpigmented, hypertrichotic patch (Figure 1), with onset in early adulthood, usually during or shortly after puberty. To help differentiate it from congenital melanocytic nevus and smooth muscle hamartoma, it is important to ask whether the lesion was present at birth or developed subsequently.

Figure 1.

Becker’s nevus presenting as a hyperpigmented and markedly hypertrichotic patch.

During puberty there is often a period of androgen-dependent lateral growth and darkening of hairs lasting for several years before stabilization. Although some patients report pruritus, the lesions are usually asymptomatic and brought to the attention of the physician for cosmetic concern.

Reported cutaneous findings within Becker’s nevi include acneiform eruptions, eczematous dermatitis, tinea versicolor, ichthyosis, and lichen planus. Patients may complain of symptoms from any of these co-localized disorders.

Characteristic findings on physical examination

On physical examination, most lesionsare localized, unilateral macules, patches, or very thin plaques. Theyare most frequently located on the shoulders, anterior chest, andscapular region, although numerous sites have been reported.

Lesionsrange in color fromlight tan to dark brown and are usually uniform inpigmentation. There is often an irregular, sharply demarcated borderthat resolves into small satellite islands of hyperpigmentation. Lesionsrange in diameter from a few centimeters to greater than 20 cm.

Hypertrichosisis a characteristic finding and tends to develop after pigmentation(sometimes up to 2 years later), with the hairs becoming coarser anddarker over time. In some cases the hypertrichosis may be subtle (Figure 2) or even absent (Figure 3).

Figure 2.

Beckers nevus with mild hyperpigmentation and scant hypertrichosis

Figure 3.

Becker’s nevus with mild breast hypoplasia without hair. Photo courtesy of Dr Sarah Dill.

Expected results of diagnostic studies

Histologicconfirmation of the diagnosis is generally unnecessary unless thelesion cannot be differentiated from a congenital melanocytic nevusbased upon clinical characteristics. Histologic findings include basalhyperpigmentation that may be subtle or easily discernible, withabnormal to minimally increased number of basilar melanocytes and noevidence ofmelanocytic nests.

There is variablehyperkeratosis, acanthosis, and elongation and focal fusion of the reteridges. The rete bases are often flattened and appear to have arectangular or square shape that is best appreciated on low-powerexamination and can help to establish the diagnosis inthe absence ofother histologic findings (Figure 4). Increased number of arrector pilimuscles may be seen and represents the smooth muscle hamartomatouscomponent of the Becker’s nevus (Figure 5).

Figure 4.

Becker’s nevus with associated smooth muscle proliferation.

Figure 5.

Becker’s nevus demonstrates fusion and flattening of the rete bases, mild hyperkeratosis, basalar hyperpigmentation and a few characteristic “rectangular” rete ridges.

Thedegree of basal pigmentation, number of hair follicles and smooth musclevaries significantly, and the biopsy may be interpreted as normal skinif the dermatopathologist is unaware of the clinical history. Inaddition, there may be a concomitant suppurative folliculitis with orwithout rupture and surrounding suppurative granulomatous inflammation.

Diagnosis confirmation

Thedifferential diagnosis includes congenital melanocytic nevus, congenitalsmooth muscle hamartoma, nevus spilus, and café au lait macules.

Congenitalmelanocytic nevi are present at birth and are typically darker incolor, raised, have no anatomic predilection and demonstrate melanocyticnevus cells on skin biopsy.

Congenital smoothmuscle hamartoma typically presents at birth or infancy as a firmskin-colored or light brown plaque. It has less prominent pigmentationand hypertrichosis when compared with Becker’s nevus, and most casesdisplay pseudo-Darier’s sign, temporary induration after rubbing thelesion. Histologically, smooth muscle hamartoma is characterized byhyperplasia of smooth muscle bundles throughout the dermis. Becker’snevus has more pronounced epidermal changes and a varying smooth musclecomponent within the dermis.

Nevus spilustypically contains several hyperpigmented macules and papules thatrepresent small melanocytic nevi distributed within a café au lait-likebackground that helps differentiate it from the uniformly pigmentedBecker’s nevus. Café au lait macules are usually smaller, lack terminalhairs and most often exhibit fairly uniform light brown color.

Who is at Risk for Developing this Disease?

The prevalence of Becker’s nevus is estimated to beapproximately 0.5% among males. The male-to-female ratio derived from reported cases is approximately 6:1. This higher male-to-female ratio has been attributed to greater recognition of lesions in males due to androgen-dependent growth. Lesions in females tend to have lighter pigmentation and absent or subtle hypertrichosis and are therefore likely to be underreported.

The lesion has been described in all races and nearly all cutaneous surfaces. Most lesions present within the first 2 decades, typically around puberty, although congenital cases have been reported. Most cases are sporadic, but several familial cases have been described.

What is the Cause of the Disease?

Etiology

The etiology of Becker’s nevus remains unclear. It is a hamartoma of ectodermal and mesodermal derivatives that is thought to be hormonally responsive given the augmented smooth muscle and peripubertal growth. Androgen receptor assays have demonstrated marked increases in the number of androgen receptors in lesional skin when compared with contralateral non-lesional skin.

Additional evidence supporting heightened sensitivity to androgens includes the findings of hypertrichosis, acanthosis, dermal thickening, sebaceous hypertrophy and co-localized acne.

Numerous cases, including two originally described by Becker, have been reported to occur after sunburn or extensive sunlight exposure and therefore this could represent an additional trigger.

Pathophysiology

Thedevelopmental anomalies associated with Becker’s nevus syndrome,including breast hypoplasia, supernumerary nipples and musculoskeletalanomalies, are similar to the spectrum seen in the epidermal nevussyndrome and suggest mosaicism. In fact, chromosomal mosaicism has beendocumented in fibroblasts derived from a Becker’s nevus in one case.

Anotherreported case of Becker’s nevus identified in early childhood wasinitially verrucous and linear before becoming hyperpigmented andhypertrichotic after puberty, suggesting an initial mosaic patternfollowing the lines of Blaschko.

Because Becker'snevus has both familial and sporadic occurrence, some authors suggest aparadominant inheritance with loss of heterozygosity resulting in amosaic population of homozygous or hemizygous cells.

Systemic Implications and Complications

The Becker’s nevus itself is a benign lesion, although an association between Becker’s nevus and developmental anomalies has been reported. By far the most commonly reported associated anomaly is ipsilateral breast hypoplasia. In one study this occurred more frequently among women than men at a ratio of approximately 4:1. The higher reported incidence among women is likely because breast hypoplasia is more conspicuous in women.

Hypoplasia of the breast can best be explained by the excess androgen receptors within lesional skin counteracting the estrogen-dependent development of breast, areola and nipple at puberty. Spironolactone treatment resulted in enlargement of the hypoplastic breast in one study.

Other reported anomalies include scoliosis, vertebral anomalies, limb asymmetry, fused or accessory ribs, facial asymmetry, odontomaxillary dysplasia, asymmetry of the scapulae, hypoplasia of the contralateral labium minus, decreased hairiness of the ipsilateral axilla, accessory scrotum, and supernumerary nipples. Similar anomalies are also seen in epidermal nevus syndromes, and some authors consider Becker’s nevus to be an organoid type of epidermal nevus sharing molecular mosaicism as the underlying etiology.

Treatment Options

Table I. Treatment options for Becker'as nevus

Table I.

Treatment options for Becker'as nevus
Medical Treatment Surgical Procedures Physical Modalities
Long-pulse alexandritelaser
Long-pulse rubylaser
Q-switched ruby laser Surgical excision Electrolysis
Q-switched Nd: YAG Waxing
Erbium-doped fiberlaser
Erbium YAG

Optimal Therapeutic Approach for this Disease

The most important step in the treatment of Becker’s nevus is establishing the diagnosis. If the lesion cannot be clinically differentiated from a congenital melanocytic nevus, skin biopsy is recommended. Treatment options are summarized in Table 1.

Evaluate the patient for commonly associated abnormalities such as breast hypoplasia and musculoskeletal anomalies. Anomalies should be investigated and treated with the relevant specialist where appropriate.

Symptomatic intralesional cutaneous lesions such as acne, eczema, tinea versicolor, and lichen planus should be identified and treated.

Although cases of malignant melanoma have been reported both intralesionally and in association with Becker’s nevus, given the high prevalence (approximately 0.52% among males), the risk of malignant transformation appears to be very low and regular surveillance is considered unnecessary.

Since the majority of lesions are asymptomatic and treatment is requested for cosmetic purposes, it is important to assess the patient’s level of concern and to weigh the risk/benefits of treatment before choosing a treatment modality. Cosmetic treatment can be divided into two components: removal of excess hair and reduction of the hyperpigmentation. If the patient is primarily concerned by the hypertrichosis, then simple waxing or electrolysis may be offered.

Long-pulsed lasers are effective in treatment of both hyperpigmentation and hypertrichosis. In one case report, 11 patients were treated with a long-pulsed alexandrite laser with a wavelength of 755nm, a pulse duration of 3ms and a fluence of 20-25J/cm2. Patients received between 2 and 12 treatments at 2-3 month intervals.

In all patients, hair density decreased and became similar to the surrounding non-lesional skin. Two patients had an excellent response to pigment clearing, five had a good response, and four had a fair response. Adverse effects of this treatment included a small hypertrophic scar in one patient and mild hypopigmentation in others that resolved over time. Another report showed similar long-term hair and pigment reduction with the use of 694-nm long-pulse ruby laser.

If the patient is primarily concerned by the hyperpigmentation, then laser therapy may be necessary. Q-switched lasers such as the Q-switched ruby, Q-switched Nd:YAG, and Q-switched alexandrite lasers selectively target epidermal and dermal melanin without removing the entire epidermis. One review article recommends 3 to10 treatments at monthly intervals with the Q-switched ruby laser at fluences between 7 and 20J/cm2. Complete clearing of the lesion is rarely achieved, hypertrichosis is unaffected, and frequent repigmentation has been reported after such treatment. Repigmentation is thought to be due to the persistence of deep hair-follicle melanocytes.

Fractional resurfacing was found to be effective and safe for lightening the pigment of Becker’s nevus in a case study of 2 male patients, but hypertrichosis was not affected. The patients were treated with a 1550nm wavelength erbium-doped fiber laser between 6 and 10mJ every 4 weeks for a total of 5 to 6 sessions. More than 75% of pigment had cleared by the 1-month follow-up in both patients.

Ablative lasers, such as the 2490nm erbium:YAG, target tissue water and remove the entire epidermis. These lasers often result in posttreatment edema, erythema, burning and crusting. Pigmentary changes, acne flares, herpes simplex infection, scars and milia are additional adverse consequences of such ablative modalities.

Surgical excision with grafting is generally not recommended because of the often large size of lesions and potential for significant scarring.

Patient Management

Becker’s nevus is a benign skin lesion, and malignant transformation, although reported, is rare. Therefore regular surveillance is unnecessary. Because the lesion is benign and typically asymptomatic, no treatment is commonly recommended.

In approaching cosmetic treatment, it is important to first discuss the risks and benefits of the above-mentioned therapies. Risks of laser therapy include scarring, hypopigmentation, change in skin texture, acne flares, milia formation, temporary burning, erythema, and crusting. These risks vary with each laser modality. The patient should be informed that complete clearance of pigmentation is uncommon and repigmentation frequently occurs.

Unusual Clinical Scenarios to Consider in Patient Management

Remember that Becker’s nevus is uncommonly associated with developmental anomalies. If such anomalies are suspected or identified, it is important to consult the relevant specialist for proper diagnosis and treatment.

What is the Evidence?

Johnson, G, Burd, R, Lebwohl, M, Heymann, WR, Jones, JB, Coulson, I. "Treatment of skin disease". St. Louis: Mosby. 2002. pp. 84-5.

(Book chapter reviewing the treatment and management of Becker’s nevus.)

Choi, JE, Kim, JW, Seo, SH, Son, SW, Ahn, HH, Kye, YCK. "Treatment of Becker’s nevi with a long-pulse alexandrite laser". Dermatol Surg. vol. 35. 2009. pp. 1105-8.

(Case report on treatment of 11 cases of Becker’s nevus with long-pulse alexandrite laser. Discussion includes current review and comparison of the risks/benefits of other treatment modalities.)

Glaich, AS, Goldberg, LH, Dai, T, Kunishige, JH, Friedman, PM. "Fractional resurfacing: a new therapeutic modality for Becker’s Nevus". Arch Dermatol. vol. 143. 2007. pp. 1488-90.

(Case report on the treatment of 2 cases of Becker’s nevus with fractional resurfacing. Discussion includes comparison of other laser treatment modalities.)

Glinick, SE, Alper, JC, Bogaars, H, Brown, JA. "Becker’s melanosis: associated abnormalities". J Am Acad Dermatol. vol. 9. 1983. pp. 509-14.

(Reviews the epidemiology of Becker’s nevus and associated abnormalities.)

Chima, KN, Janniger, CK, Schwartz, RA. "Becker’s melanosis". Cutis. vol. 57. 1996. pp. 311-4.

(Comprehensive review article of Becker’s nevus.)

Becker, SW. "Concurrentmelanosis and hypertrichois in distribution of nevus unius lateris". Arch DermSyphilol. vol. 60. 1949. pp. 155-60.

(First reported description of Becker’s nevus.)

Danarti, R, Konig, A, Salhi, A, Bittar, M, Happle, R. "Becker's nevus syndrome revisited". J Am Acad Dermatol. vol. 51. 2004. pp. 965-9.

(Review of developmental anomalies associated with Becker’s nevus. Includes discussion of the pathogenesis and genetic basis for Becker’s nevus.)

Happle, R. "Paradominant inheritance: a possible explanation for Becker's pigmented hairy nevus". Eur JDermatol. vol. 2. 1992. pp. 39-40.

(Discussion of the proposedgenetic basis for both familial and sporadic Becker’s nevi.)Special thanks to Dr Sarah Dill, Dr Jennifer Jenkins and Dr Gary Kantor for contributing photographs for this publication
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