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Nevus sebaceus
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Nevus sebaceus (NS), first described by Jadassohn in 1895, is a term for a congenital hamartoma of the epidermis and adnexal structures typically involving the scalp and face. It results from the mosaic expression of HRAS and KRAS gene mutations. It presents at birth or appears in early childhood as a pink, orange, or yellow waxy plaque with a granular pitted surface that is often hairless. The size and configuration can be variable. During puberty the lesion thickens and becomes verrucous as glands enlarge within the dermis. Development of cutaneous and adnexal neoplasms has been reported in 10%–20% of lesions after puberty and in adulthood. These neoplasms are most commonly benign, although multiple benign and malignant neoplasms may arise concomitantly within a single lesion. Rarely, NS may occur as part of an epidermal nevus syndrome, such as phakomatosis pigmentokeratotica or Schimmelpenning syndrome, resulting in neurological, ophthalmological, and musculoskeletal abnormalities. Surgical treatment addresses cosmetic issues, as well as prophylaxis or treatment of neoplasms.
Management Strategy
For most lesions, clinical examination is sufficient to establish the diagnosis. A skin biopsy can confirm the clinical impression when indicated. Most neoplastic growths that arise in a NS do not develop until after the age of 16 years and the overwhelming majority are benign. These include syringocystadenoma; papilliferum; trichoblastoma; trichilemmoma; sebaceoma; nevocellular nevus; apocrine cystadenoma; and seborrheic keratosis. The most common malignancy that develops within a NS is a basal cell carcinoma, but the absolute incidence is very rare. Isolated case reports describe rare patients who have developed sebaceous carcinoma, squamous cell carcinoma, trichilemmal carcinoma, or microcystic adnexal carcinoma within a NS.
In 2000, a case series established that trichoblastoma was the most common neoplasm arising in NS. With this evidence of minimal risk of malignant neoplastic transformation, prophylactic surgery is not justified. Conservative management with clinical observation and biopsy of any lesions suspicious for malignancy appear to be most prudent.
Tumors arising in nevus sebaceus: a study of 596 cases
Cribier B, Scrivener Y, Grosshans E. J Am Acad Dermatol 2000; 42: 263–8.
Retrospective case series of 596 cases demonstrating a 1.7% occurrence of benign tumors in childhood. Most tumors arising in NS occurred in adults over 40; in these adults, 2.1% of the neoplasms were basal cell carcinomas. The authors conclude that prophylactic surgery in children is of uncertain benefit.
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