3.2.1 Seborrhoeic Keratosis
Grading & Level of Importance: B
Seborrhoeic wart, basal cell papilloma.
90% of older people > 60 years. The seborrheic keratosis is the most frequent benign skin tumour.
The seborrheic keratosis is a benign verrucous epithelial tumour, commonly seen in older patients.
Aetiology & Pathogenesis
The cause of seborrheic keratosis is not completely known. Stable and clonal mutations or activation of FRFR3, PIK3CA, RAS, AKT1 and EGFR genes are found in seborrhoeic keratoses.
Signs & Symptoms
It is a soft, wart-like (verrucous), keratotic yellowish to brown or black papule or plaque of the skin. The lesions can vary in size from a few millimetres to several centimetres. They are sometimes itchy.
Seborrheic keratoses can be localized on all areas of the body, most often on trunk and face. Dermatome-like pattern may occur.
Exophytic or flat subtypes. Stucco keratosis and black papular dermatitis (dermatosis papulosa nigra) are variants of seborrheic keratosis.
Laboratory & other workups
Laboratory tests are not needed for the diagnosis.
Major criteria are acanthosis, hyperkeratosis and horn pseudo-cysts, usually accompanied by epidermal hyperpigmentation.
Seborrhoeic keratoses show slow growth, and may reach several centimetres in size and become numerous. Leser-Trélat sign is the extremely rare explosive onset of multiple seborrheic keratoses in a segmental like pattern, and may indicate an underlying solid tumour.
Seborrheic keratoses may sometimes become irritated, infected or be bleeding (trauma). Malignant transformation is extremely rare.
Seborrheic keratoses can be identified by clinical features. Dermoscopy is helpful in visualising the horn pearls. Histology is generally not necessary except melanoacanthoma type.
It is important to distinguish seborrheic keratoses from other new pigmented lesions (melanoma, pigmented basal cell carcinoma, melanocytic naevus, longstanding black angioma).
Prevention & Therapy
Treatment of seborrheic keratosis is generally not needed except in severely symptomatic lesions or in specific localizations or disfiguring patterns. Treatment options include curettage, cryosurgery, laser ablation, shave excision.
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