An Atlas of Lumps and Bumps, Part 35: Nevus Sebaceous

Nevus Sebaceous

Nevus sebaceous, also known as nevus sebaceous of Jadassohn, is a hamartoma of the skin, and its adnexa is characterized by hyperplasia of the epidermis, immature hair follicles, and abnormalities of both the sebaceous and apocrine glands.^1-5 Because the lesion involves more than just a sebaceous component, the more encompassing term “organoid nevus” has also been used to describe this condition.^6,7

Nevus sebaceous occurs in approximately 0.1% to 0.3% of all newborns.^1-5 Both sexes are equally affected.^8,9 There is no racial and/or ethnic predominance.^9,10 The occurrence of the nevus is usually sporadic, but familial cases have been reported.⁵

The exact pathogenesis is not known. Presumably, nevus sebaceous develops from pluripotent primary epithelial germ cells, which have the potential to differentiate into various neoplasms.⁸ Nevus sebaceous is thought to be caused by postzygotic mosaic mutations in the HRAS or KRAS genes (located on the short arm of chromosome 11 and 12, respectively).^5,11,12

Approximately two-thirds of cases are present at birth, with the remaining developing in early childhood.^1-3 At birth, or shortly thereafter, nevus sebaceous generally presents as a solitary, well-circumscribed, smooth to velvety, yellow-orange or tan, round or oval, minimally raised hairless plaque (Figure 1).^6,10

Fig. 1. Nevus sebaceous is a skin hamartoma, characterized by hyperplasia of the epidermis, immature hair follicles, and sebaceous and apocrine gland abnormalities.

The scalp followed by the face are sites of predilection.^6,10 Rarely, the trunk and extremities may also be affected.⁴ Lesions on the scalp are classically associated with overlying partial or total alopecia.^4,9,10 In infancy and early childhood, lesions remain mostly unchanged due to the quiescence of sebaceous glands.⁵ With time, lesions tend to be more elevated and increase in size proportional to the body size (Figure 2).⁷


Fig. 2 Lesions tend to be more elevated and increase in size.

At or just before puberty, possibly because of hormonal influence on sebaceous and apocrine glands, the lesion grows rapidly and acquires a verrucous or even a nodular appearance (Figure 3).^4,10,13


Fig. 3. At or just before puberty, the lesion grows rapidly and acquires a verrucous or even a nodular appearance.

The lesion is usually unilateral and rarely on multiple locations or bilateral.^14,15 A variant characterized by large, pedunculated or verrucous, pink nodules or tumors in the neonatal period has been described.^16,17 Cerebriform nevus sebaceous is a rare variant of nevus sebaceous characterized by a cerebriform appearance of the lesion similar to a human brain due to numerous gyri and sulci (Figure 4)^18,19

Fig. 4. Cerebriform nevus sebaceous is a rare variant of nevus sebaceous characterized by a cerebriform appearance of the lesion similar to a human brain.

Nevus sebaceous is typically asymptomatic and an isolated finding.^1-3.9.20 If the nevus sebaceous (linear distributed along the lines of Blaschko) is accompanied by ocular (eg, coloboma, choristoma) and neurologic (eg, ipsilateral hemimegalencephaly, agenesis of the corpus callosum, Dandy-Walker syndrome, focal seizures, intellectual disability) abnormalities, it is referred to as linear sebaceous nevus syndrome, Schimmelpenning syndrome or Schimmelpenning-Feuerstein-Mims syndrome.^5,21,22 Other features of the syndrome include skeletal defects (scoliosis, vitamin D-resistant rickets, dental irregularities), cardiovascular abnormalities (ventricular septal defect, coarctation of the aorta, aortic hypoplasia) and urologic abnormalities (horseshoe kidneys, duplicated urinary collecting system).^1-3,21-24

The diagnosis is usually clinically based on the characteristic features. Typical dermoscopic findings include yellowish or brownish globules aggregated in clusters on yellow background, white-yellow lobular aspect, yellow-grayish papillary appearance, or homogenous yellowish appearance, and peripheral vascularization (fine linear irregular or arborescent vessels).^20,25 A tissue biopsy should be considered if the diagnosis is in doubt. Prenatal diagnosis is feasible by ultrasonography for large and exophytic lesions.²⁶

The lesion can be aesthetically unappealing, especially when it occurs on the face. Children born with a large nevus sebaceous are at increased risk of other developmental defects.¹⁷ Nevus sebaceous may be complicated by the development of benign and malignant nevoid tumors in the original nevus.⁴ Neoplasms occur mostly in the fourth decade of life in approximately 10 to 30% of lesions.^6,8 The majority of these tumors are benign; less than 1% of nevus sebaceous is complicated by malignant tumors.^1-3 The most common benign tumor is trichoblastoma, followed by syringocystadenoma papilliferum.^{1-3,5,6,20,27} Other benign tumors include trchilemmoma, trichoepithelioma, sebaceous adenoma, sebaceous epithelioma, apocrine cystadenoma, apocrine hidrocystoma, hidradenoma, eccrine poroma, spiradenoma, and syringoma.^8,28-31 Malignancy is suggested by the acute appearance of a large, discrete, ulcerating papule or nodule within the lesion.⁶ The risk of malignancy increases with age and is very rare in children.^5,11 The most common malignant tumor is basal cell carcinoma.^28,32-34 Other malignant tumors include squamous cell carcinoma, apocrine carcinoma, ductal adenocarcinoma, porocarcinoma, anaplastic adnexal carcinoma, trichilemmal syringomatous carcinoma, and sebaceous carcinoma.^8,30,35 Although very rare, multiple tumors arising in a nevus sebaceous have been reported.^36,37

AFFILIATIONS:
¹Clinical Professor of Pediatrics, the University of Calgary, Calgary, Alberta, Canada
²Pediatric Consultant, the Alberta Children’s Hospital, Calgary, Alberta, Canada
³Dermatologist, Medical Director and Founder, the Toronto Dermatology Centre, Toronto, Ontario, Canada
⁴Associate Clinical Professor of Pediatrics, Dermatology and Skin Sciences, the University of British Columbia, Vancouver, British Columbia, Canada.
⁵Pediatric Dermatologist, the Pediatric Institute, Kuala Lumpur General Hospital, Kuala Lumpur, Malaysia

CITATION:
Leung AKC, Barankin B, Lam JM, Leong KF. An Atlas of Lumps and Bumps, Part 35: Nevus Sebaceous. Consultant. 2023;64(1):e4. doi:10.25270/con.2024.01.000003

CORRESPONDENCE:
Alexander K. C. Leung, MD, #200, 233 16th Ave NW, Calgary, AB T2M 0H5, Canada (aleung@ucalgary.ca)

EDITOR’S NOTE:
This article is part of a series describing and differentiating dermatologic lumps and bumps. To access previously published articles in the series, visit: https://www.consultant360.com/resource-center/atlas-lumps-and-bumps.