Seborrhoeic keratosis
Definition
Seborrhoeic keratosis is a benign intraepidermal neoplasm that most commonly occurs in ageing skin.
Synonyms
Senile wart; seborrhoeic wart
Epidemiology
These lesions are very common. In an Australian population, seborrhoeic keratoses were present in 12% of people aged 15—25 years, 79% of people aged26—50 years, and 100% of people aged years. The lesions increase in number with age and are found less commonly in more-pigmented skin. There is no apparent sex predilection.
Etiology
Ultraviolet (UV) radiation exposure is related to the etiology of some seborrheic keratoses. Other possible causes under investigation include genetic and metabolic factors.
Localisation
Seborrhoeic keratoses have a predilection for the trunk, head, and neck, but can occur on any skin surface other than the palms, soles, and mucosal surfaces. They tend to group together in skin creases, such as under the breast or in the groin.
Clinical features
Seborrhoeic keratoses typically present as solitary or multiple flat-based papules or plaques with a filiform surface. A brown or black appearance is typical, but some lesions are pale or Grey. Macular seborrhoeic keratoses remain thin, with subtle scale. Stucco keratoses, which are considered a variant of seborrhoeic keratosis, form distinctive small keratoses that are largely restricted to the lower limbs. Dermoscopy reveals multiple brown or white clods, representing plugs of keratin, and thick ridges imparta cerebriform pattern. The acute appearance of multiple seborrhoeic keratoses associated with an internal malignancy is called the Leser Trélat sign.
Histogenesis
Seborrhoeic keratoses arise from epidermal keratinocytes. They have an increased proliferation rate and decreased apoptosis compared with normal keratinocytes.
Genetic profile
Somatic mutations are seen in FGFR3, PIK3CA, the TERT promoter, the DPH3promoter, BRAS, KRAS, EGER, and AKTI.
Prognosis and predictive factors
Seborrhoeic keratoses are benign, but a search for internal malignancy should be performed in response to the sudden appearance of multiple lesions.
Reference:
WHO classification of skin tumours, 4th edition (2018): 57-60.