Seborrheic keratosis
Template:Short description Template:Distinguish Template:Infobox medical condition (new) 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.<ref name="cleve">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="mayosymp">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
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 Template:Convert across.<ref name=mayosymp/> They are often associated with other skin conditions, including basal cell carcinoma.<ref>Template:Cite journal</ref> Sometimes, seborrheic keratosis and basal cell carcinoma occur at the same location.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> At clinical examination, a differential diagnosis considers warts and melanomas.<ref name="cleve" /> 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.<ref>Template:Cite journal</ref>
Cause
The cause of seborrheic keratosis is not known. The only definitive association is that its prevalence increases with age.<ref name="cleve" />
Diagnosis
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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.<ref>Template:Cite journal</ref> 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.Template:Citation needed
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.<ref>Template:Cite journal</ref> To date, the gold standard in the diagnosis of seborrheic keratosis is represented by the histolopathologic analysis of a skin biopsy.<ref>Template:Cite book</ref>
Subtypes
Seborrheic keratoses may be divided into the following types:<ref name="Fitz2"/><ref>Template:EMedicine</ref><ref name="EMedicine Stucco">Template:EMedicine</ref>
| Subtype (and alternative names) | Characteristics | Image |
|---|---|---|
| Common seborrheic keratosis (basal cell papilloma, solid seborrheic keratosis) | Dull or lackluster surface.<ref name="Fitz2"/>Template:Rp | |
| Reticulated seborrheic keratosis (adenoid seborrheic keratosis) | Dull or lackluster surface, and with keratin cysts seen histologically.<ref name="Fitz2"/>Template:Rp | |
| Stucco keratosis (deratosis alba,<ref name="Bolognia">Template:Cite book</ref> digitate seborrheic keratosis, hyperkeratotic seborrheic keratosis, serrated seborrheic keratosis, verrucous seborrheic keratosis) | Common. Dull or lackluster surface, and with church-spire-like projections of epidermal cells around collagen seen histologically.<ref name="Fitz2"/><ref name="Andrews"/> Stucco keratoses are often light brown to off-white, and are no larger than a few millimeters in diameter. They are often found on the distal tibia, ankle, and foot.<ref name="EMedicine Stucco"/> | |
| Clonal seborrheic keratosis | Dull or lackluster surface, and with round, loosely packed nests of cells seen histologically.<ref name="Fitz2"/>Template:Rp | |
| Irritated seborrheic keratosis (inflamed seborrheic keratosis, basosquamous cell acanthoma) | Dull or lackluster surface.<ref name="Fitz2"/>Template:Rp | |
| Seborrheic keratosis with squamous atypia | Dull or lackluster surface, and with round, loosely packed nests of cells seen histologically.<ref name="Fitz2"/>Template:Rp | |
| Melanoacanthoma (pigmented seborrheic keratosis) | Dull or lackluster surface.<ref name="Fitz2"/>Template:Rp<ref name="Andrews"/>Template:Rp It involves a proliferation of keratinocytes and melanocytes.<ref name="urlCutaneous Melanoacanthoma: eMedicine Dermatology">{{#invoke:citation/CS1|citation | CitationClass=web
}}</ref> |
| Inverted follicular keratosis<ref group="notes">Inverted follicular keratosis is generally thought to be a rare variant of seborrheic keratosis, but this position is not universally accepted. - Template:Cite journal</ref> |
Asymptomatic, firm, white–tan to pink papules<ref name="Bolognia"/> Microscopically it is characterized as a well-circumscribed inverted acanthotic squamous proliferation containing squamous eddies and without significant atypia.<ref>Template:Cite journal</ref> | 
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Differential diagnoses
Dermatosis papulosa nigra (DPN) is a condition of many small, benign skin lesions on the face, a condition generally presenting on darker-skinned individuals.<ref name="Andrews"/>Template:Rp DPN is extremely common, affecting up to 30% of black people in the United States.<ref name="ReferenceA">Template:Cite journal</ref>
Treatment
Medical reasons for removing seborrheic keratoses include irritation and bleeding. They may also be removed for cosmetic reasons.<ref name="cleve"/><ref name="mayosymp"/> Generally, lesions can be treated with electrodesiccation and curettage, or cryosurgery. When correctly performed, removal of seborrheic keratoses will not cause much visible scarring.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Epidemiology
Seborrheic keratosis is the most common benign skin tumor. Incidence increases with age. There is less prevalence in people with darker skin.<ref name="Zhang2011">Template:Cite journal</ref> In large-cohort studies, all patients aged 50 and older had at least one seborrheic keratosis.<ref>Template:Cite journal</ref> Onset is usually in middle age, although they are common in younger patients too, as they are found in 12% of 15-year-olds to 25-year-olds, which makes the term "senile keratosis" a misnomer.<ref>Template:Cite journal</ref>
See also
Notes
References
External links
Template:Sister project Template:Medical resources Template:Diseases of the skin and appendages by morphology Template:Cutaneous ketatosis, ulcer, atrophy, necrobiosis, and vasculitis Template:Skin tumors, epidermis