Sebaceus and Becker's Nevus: Overview of Their Presentation, Pathogenesis, Associations, and Treatment.

Nevus sebaceus (NS) and Becker's nevus (BN) are two variants of epidermal nevi. NS clinically presents as a yellowish-orange, hairless plaque on the scalp, face, or neck, while BN presents as a tan-to-brown hyperpigmented, sometimes hypertrichotic, plaque typically on the chest and shoulder. Histologically, NS displays mature or nearly mature sebaceus glands as well as acanthosis and fibroplasia of the papillary dermis. BN shows variable papillomatosis, acanthosis, and hyperkeratosis, with hyperpigmentation of the basal/suprabasal layer. While the genetic basis of NS is thought to be due to post-zygotic mutations in the Harvey rat sarcoma viral oncogene homolog (HRAS)/Kristen rat sarcoma viral oncogene homolog (KRAS) genes, the genetic basis of BN is relatively unknown and is implicated with paradominant inheritance. In some patients, NS and BN can each be associated with additional cutaneous and extra-cutaneous anomalies, ranging from benign or malignant tumors to multiple organ irregularities. Due to the wide range of possible associations, treatment for NS and BN is devised on a case-by-case basis. In this article, we review the features, etiology, and diagnosis/management of NS and BN, with a focus on associations. We also report a patient who concomitantly presents with both lesions.