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Concept
Kératose séborrhéique
Résumé
A seborrheic keratosis is a non-cancerous (benign) skin tumour that originates from cells, namely keratinocytes, in the outer layer of the skin called the epidermis. Like liver spots, seborrheic keratoses are seen more often as people age.
The tumours (also called lesions) appear in various colours, from light tan to black. They are round or oval, feel flat or slightly elevated, like the scab from a healing wound, and range in size from very small to more than across. They are often associated with other skin conditions, including basal cell carcinoma. Rarely seborrheic keratosis and basal cell carcinoma occur at the same location. At clinical examination the differential diagnosis include a wart and melanoma. Because only the top layers of the epidermis are involved, seborrheic keratoses are often described as having a "pasted on" appearance. Some dermatologists refer to seborrheic keratoses as "seborrheic warts", because they resemble warts, but strictly speaking the term "warts" refers to lesions that are caused by the human papillomavirus.
The cause of seborrheic keratosis is not known. The only definitive association is that its prevalence increases with age.
Visual diagnosis is made by the "stuck on" appearance, horny pearls or cysts embedded in the structure. Darkly pigmented lesions can be challenging to distinguish from nodular melanomas. Furthermore, thin seborrheic keratoses on facial skin can be very difficult to differentiate from lentigo maligna even with dermatoscopy. Clinically, epidermal nevi are similar to seborrheic keratoses in appearance. Epidermal nevi are usually present at or near birth. Condylomas and warts can clinically resemble seborrheic keratoses, and dermatoscopy can be helpful to differentiate them. On the penis and genital skin, condylomas and seborrheic keratoses can be difficult to differentiate, even on biopsy.
A study examining over 4,000 biopsied skin lesions identified clinically as seborrheic keratoses showed 3.1% were malignancies. Two-thirds of those were squamous cell carcinoma.
Source officielle
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