3.1.5 Naevus sebaceous
Grading & Level of Importance: C
Naevus sebaceous of Jadassohn.
Affects 0.3% of newborns. The prevalence is equal in males and females. Most frequent scalp lesion in newborns and childhood.
A congenital epidermal hamartoma that comprises sebaceous, follicular, and apocrine elements.
Aetiology & Pathogenesis
Postzygotic somatic mutations of the Ras gene family, most commonly HRAS,less common KRAS.
Signs & Symptoms
At birth: a slightly raised, solitary plaque with a smooth, yellowish surface. Most commonly present on the scalp ,hairloss at the site. At puberty, the lesion becomes thicker, and the surface is more verrucous. In adulthood, neoplasms (most commonly benign) may develop within the lesion.
Most commonly scalp area (90%), but it may also appear on the face and neck and rarely on the trunk.
None. Association with syndromal constellation: Schimmelpenning-Feuerstein-Mims syndrome, Didymosis aplasticosebacea.
Laboratory & other workups
Not necessary. Genetic counselling may be necessary in some cases.
In infancy: epidermal changes include acanthosis and papillomatosis; pilosebaceous units are immature. At puberty: the epidermis becomes more hyperplastic, papillomatous, and verrucous. Numerous sebaceous glands with an increased number of sebaceous lobules are found in the superficial dermis.
In adulthood, secondary neoplasms may develop. The most common tumour within the naevus sebaceous is trichoblastoma, followed by syringocystadenoma papilliferum. Basal cell carcinoma develops in less than 1% of lesions.
History; clinical features.
In early infancy: aplasia cutis congenita, mastocytoma. In later stages: epidermal nevus, congenital nevus, sebaceoma, seborrheic keratosis, verruca vulgaris, juvenile xanthogranuloma.
Prevention & Therapy
Observation, surgical excision (depending on the size and location of the tumour).
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