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Synonyms: naevus sebaceous, naevus sebaceous of Jadassohn, verrucous epidermal naevus, organoid naevus. Note the American spelling 'nevus'.
A sebaceous naevus is a congenital skin lesion which usually manifests as a bald patch on the scalp of the baby. The area of hair loss looks orange or yellowish, with a velvety feel and appearance. It is usually oval or circular. In adolescence, under the influence of sex hormones, it becomes bumpy and warty, with an unpleasant verrucoid appearance.
Throughout teenage years and early adulthood they usually stay quiescent. Sometimes they enlarge in later adulthood and, rarely, undergo neoplastic change which on the whole involves benign tumours.
Sebaceous naevi are hamartomas, meaning they arise from tissues normally found at that site but they grow in a disorganised way. They have a common embryological origin of the pilosebaceous-apocrine unit and therefore contain sebaceous glands, hair follicles and sweat glands. Hence the term sebaceous naevus is a little inaccurate: some pathologists prefer the term verrucous epidermal naevus or organoid naevus. Although they contain elements of hair follicles, normal terminal hair follicles are absent making the area look hairless. Most are solitary, with the scalp being the most common site.
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Estimated prevalence is 0.3% of all newborns worldwide, with an equal sex distribution.
- Usually, a single hairless patch (round or linear) is noted on the scalp at birth, or shortly thereafter.
- The classical velvety tan or yellow-orange appearance may be noted.
- The lesion may appear more prominent in newborns, due to the effects of maternal sex hormones.
- In adolescents the lesion tends to take on its nodular verrucoid appearance due to the influence of sex hormones.
- In later life there may be overgrowth of components of the lesion indicating possible benign or malignant tumours developing within the lesion.
The appearance of sebaceous naevi is fairly characteristic but the following lesions may have a similar appearance or affect similar areas of the body:
- Aplasia cutis congenita
- Naevus syringocystadenomatosus papilliferous
- Juvenile xanthogranulomata
- Solitary mastocytoma
- Other causes of alopecia
Biopsy may be considered for diagnostic purposes or to investigate the nature of tumours that arise within them.
About a third of people with a sebaceous naevus have systemic abnormalities affecting the brain, eye or skeletal systems. When these occur it is termed sebaceous naevus syndrome. In these cases the naevi follow the lines of Blaschko; the more extensive the cutaneous involvement, the greater the risk of extracutaneous manifestations. Subsequent problems can include infantile epilepsy, developmental delay and intellectual disability.
- Due to the difficulty of quantifying the risk of malignant transformation, some specialists advocate full-thickness skin excision before adolescence. Others recommend watchful waiting .
- Some cases will in any case not be suitable for excision due to their size and location. These should be subjected to regular review.
- Photodynamic therapy can play a role in removing the lesion.
- Seek the advice of a dermatologist and/or plastic surgeon to help decide on the need for, and timing of, excision.
- Any lesion that changes its appearance significantly, ulcerates, becomes painful, bleeds or shows other signs of potential malignancy, should be referred to a dermatologist.
- Poor cosmetic appearance.
- Development of a benign or malignant tumour within the lesion.
- Complications associated with removal of the lesion.
Of these 15%, 80% develop foci of benign neoplasms such as trichoblastomas and syringocystadenomas. The remaining 20% develop malignant changes, with basal cell carcinomas making up half of those, squamous cell carcinomas a quarter.
Usually any malignant change occurs in adulthood but it has been reported in children as young as 8 years. Malignancy can be diagnosed in the same way as other malignant skin tumours, with dermoscopy playing its usual role.
Further reading and references
; DermNet NZ
; Clinicopathologic analysis of 21 cases of nevus sebaceus: a retrospective study. Indian J Dermatol Venereol Leprol. 2008 Nov-Dec74(6):625-7.
; Nevus sebaceous revisited. Pediatr Dermatol. 2012 Jan-Feb29(1):15-23. doi: 10.1111/j.1525-1470.2011.01562.x. Epub 2011 Oct 13.
; Epidermal nevus syndrome. Handb Clin Neurol. 2013111:349-68. doi: 10.1016/B978-0-444-52891-9.00041-5.
; Epidermal nevus syndromes. Handb Clin Neurol. 2015132:291-316. doi: 10.1016/B978-0-444-62702-5.00022-6.
; DermNet NZ
; Management of nevus sebaceous and the risk of Basal cell carcinoma: an 18-year review. Pediatr Dermatol. 2009 Nov-Dec26(6):676-81. doi: 10.1111/j.1525-1470.2009.00939.x. Epub 2009 Jul 20.
; The use of photodynamic therapy in dermatology. G Ital Dermatol Venereol. 2010 Oct145(5):613-30.
; Secondary neoplasms associated with nevus sebaceus of Jadassohn: a study of 707 cases. J Am Acad Dermatol. 2014 Feb70(2):332-7. doi: 10.1016/j.jaad.2013.10.004. Epub 2013 Nov 20.
; Tumors arising in nevus sebaceus: A study of 596 cases. J Am Acad Dermatol. 2000 Feb42(2 Pt 1):263-8.
; Basal cell carcinoma appearing in a facial nevus sebaceous of Jadassohn: dermoscopic features. An Bras Dermatol. 2012 Jul-Aug87(4):640-2.