Unusual skin lesion in a teenaged boy

THE CASE

The mother of a healthy 15-year-old boy brings him to the office for evaluation of a darkening hairy patch on his left upper chest and shoulder. The patch is not symptomatic, and it first appeared as a subtle, poorly defined brown area when he was aged 10 years. 

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DIAGNOSIS: BECKER NEVUS

Discussion

Also known as Becker melanosis or Becker pigmentary hamartoma, a Becker nevus (BN) is an acquired benign hamartoma. Although the exact cause is unknown, BN has been described in both sporadic and familial cases by a paradominant mode of inheritance.^1-3 It occurs at an incidence of 0.5% in adolescent males with a 6:1 male predominance.² Approximately half of BN cases begin to develop before age 10 years.

It is hypothesized that these nevi have an increased number of androgen receptors, which can explain the typical history of onset around puberty and hypertrichosis of the nevus.² The nevi most commonly occur unilaterally on the shoulder or back. Lesions can appear as a macule or plaque and can be smooth or verrucous textured; range in color from skin colored to brown; and vary from 1 cm to many centimeters in size. They are generally irregularly shaped but well demarcated.

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Becker nevi typically last for a lifetime, but many fade with time. They are benign and have not been reported associated with malignant transformation.² Although a BN can be an isolated cutaneous finding, many associated cutaneous, muscular, and skeletal anomalies have been reported. These include, but are not limited to, tinea versicolor, eczema, acne vulgaris, acanthosis nigricans, neurofibromatosis type 1, hypoplasia of the ipsilateral breast, scoliosis, lumbar spina bifida, and pectus carinatum.^1-3

Becker nevus syndrome occurs when there are associated cutaneous, muscular, or skeletal abnormalities or unilateral breast hypoplasia in addition to the nevus.^1-3 Not surprisingly, acanthosis nigricans was appreciated during this patient’s physical exam, and he has a past medical history of eczema.

Diagnosis is usually made by history and physical examination in a patient who has a hyperpigmented patch with hypertrichosis on the shoulder or back. Differential diagnosis includes café au lait spots, postinflammatory hyperpigmentation, congenital melanocytic nevus, and plexiform neurofibroma 1 (Table).² Congenital smooth muscle hamartoma is actually the newborn equivalent of a BN with similar clinical and histological findings at birth. Histopathology shows epidermal papillomatosis, horn cysts, acanthosis, and hyperkeratosis. Often there are increased numbers of thickened smooth muscle bundles that connect to hair follicles.^1,2 There are no nevomelanocytes present, helping to distinguish this from a congenital nevomelanocytic nevus.² Although the basal cell keratinocytes are filled with melanin, there is no increase in the number of melanocytes present.

NEXT: What are the treatment options?

Because of the association with rare muscular, skeletal, and cutaneous abnormalities, further evaluation should be considered when a patient is diagnosed with a BN.^1,2 Although a biopsy is not required to make the diagnosis, biopsies are performed on occasion to rule out other etiologies. Because the lesions are benign, no treatment is required. However, for irritation or cosmetic reasons, laser therapy can be used to remove hair and lighten the lesions. Newer studies have revealed that using low-fluence high-repetition-rate diode lasers (808-801 nm) can provide significant hair reduction at 6 and 12 months posttreatment providing substantial aesthetic improvement of the lesion.⁴

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There also have been reports of the use of topical flutamide therapy for 8 weeks to treat the hyperpigmentation in the lesion.⁵ With this treatment, no change in the pigmentation of the surrounding skin outside the nevus was reported. However, there was no observed improvement in the hypertrichosis. Spironolactone also has been reported as a treatment for a case of BN with ipsilateral breast hypoplasia.⁶ In this report, the patient had enlargement of the hypoplastic breast after 1 month of taking spironolactone. Both cases help to support the association with increased androgen receptors in BN.^5,6

Conclusion

Becker nevi are probably more common than appreciated because of underreporting. It is imperative that clinical practitioners accurately identify this skin lesion in order to reassure the patient and family; recognize associated cutaneous, muscular, and skeletal anomalies; and refer appropriately to subspecialists if needed. Patients typically present with complaints related to hypertrichosis and hyperpigmentation. Although the lesions can be quite large and cosmetically concerning, reassurance should be provided that BN represents a benign entity and malignant conversion has not been demonstrated. A variety of therapeutic interventions for BN are available; however patients should be counseled that these are primarily for cosmetic improvement only.

Patient follow-up

The patient was referred to pediatric dermatology who confirmed the diagnosis of BN. Dermatology educated the family on this diagnosis and confirmed that no other associated anomalies were present on his physical examination. Because the patient was not concerned with the hyperpigmentation or hypertrichosis, no treatment was recommended at this time. Dermatology recommended follow-up annually for surveillance of the lesion and routine skin checks.

REFERENCES

1. Patel P, Malik K, Khachemoune A. Sebaceus and Becker's nevus: overview of their presentation, pathogenesis, associations, and treatment. Am J Clin Dermatol. 2015;16(3):197-204.

2. Benign dermal proliferations. In: Shou-Mei Kane K, Lio PA, Stratigos AJ, Johnson RA. Color Atlas and Synopsis of Pediatric Dermatology. 2nd ed. China: McGraw-Hill Medical; 2009:195-197.

3. Kar S, Preetha K, Yadav N, Madke B, Gangane N. Becker's nevus with neurofibromatosis type 1. Ann Indian Acad Neurol. 2015;18 (1):90-92.

4. Lapidoth M, Adatto M, Cohen S, Ben-Amitai D, Halachmi S. Hypertrichosis in Becker’s nevus: effective low-fluence laser hair removal. Lasers Med Sci. 2014;29(1):191-193.

5. Taheri A, Mansoori P, Sandoval LF, Fieldman SR. Treatment of Becker nevus with topical flutamide. J Am Acad Dermatol. 2013;69(3):e147-e148.

6. Hoon Jung J, Chan Kim Y, Joon Park H, Woo Cinn Y. Becker’s nevus with ipsilateral breast hypoplasia: improvement with spironolactone. J Dermatol. 2003;30(2):154-156.

Dr Michel is a pediatric resident, University of Florida College of Medicine, Gainesville. Drs Wheeler, Otero, Carswell, and Posa are assistant professors of Pediatrics, Division of General Academic Pediatrics, Department of Pediatrics, University of Florida College of Medicine, Gainesville. Dr Kelly is clinical associate professor of Pediatrics, Division of General Academic Pediatrics, Department of Pediatrics, University of Florida College of Medicine, Gainesville. The authors have nothing to disclose in regard to affiliations with or financial interests in any organizations that may have an interest in any part of this article.