Multiple seborrheic keratoses on the dorsum of a patient with Leser–Trélat sign.
|Classification and external resources|
A seborrheic keratosis (also known as "seborrheic verruca" and "senile wart":767:637) is a benign skin tumor that originates from keratinocytes. Like liver spots, seborrheic keratoses are seen more often as people age.
The lesions appear in various colors, 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 2.5 centimetres (1 in) across. They can often come in association with other skin conditions, including basal cell carcinoma,  as a collision tumor or by means of tumor progression phenomena. At clinical examination the differential diagnosis include, warts (though they have no viral origins) and melanoma (though they are unrelated to 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"; these lesions, however, are usually not associated with HPV, and therefore such nomenclature is discouraged.[by whom?]
Seborrheic keratoses may be divided into the following types::769–770
- Common seborrheic keratosis (basal cell papilloma, solid seborrheic keratosis)
- Reticulated seborrheic keratosis (adenoid seborrheic keratosis)
- Stucco keratosis (digitate seborrheic keratosis, hyperkeratotic seborrheic keratosis, serrated seborrheic keratosis, verrucous seborrheic keratosis) -- Often are light brown to off-white. Pinpoint to a few millimeters in size. Often found on the distal tibia, ankle, and foot.
- Clonal seborrheic keratosis
- Irritated seborrheic keratosis (basosquamous cell acanthoma, inflamed seborrheic keratosis)
- Seborrheic keratosis with squamous atypia
- Melanoacanthoma (pigmented seborrheic keratosis)
- Dermatosis papulosa nigra—Commonly found among adult dark-skinned individuals, presents on the face as small benign papules from a pinpoint to a few millimeters in size.
- Inverted follicular keratosis
Seborrheic keratosis is the most common benign skin tumor with increasing indidence in elderly individuals and no predilection of genre. There is less prevalence in people with darker skin.According to large-cohort studies, 100% of the over-50-year-old patients harbored at least one seborrhoeic keratosis. Onset is usually in middle age, although they are a common finding in younger patients—found in 12% of 15-year-olds to 25-year-olds—making the term "senile keratosis" a misnomer.
The etiology of seborrheic keratosis is poorly understood. It has been hypothesized that, since seborrheic keratosis often occurs on sun-exposed areas, ultraviolet light might be involved in their pathogenesis. However, these lesions can also be found on skin that has not been exposed to the sun. Recent insights in the biology of seborrheic keratosis have been provided by the identification of somatic mutations in FGFR3, a growth factor receptor, in the cells composing the lesion.
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. On the penis and genital skin, condylomas and seborrheic keratoses can be difficult to differentiate, even on biopsy.
To date, the gold standard in the diagnosis of seborrheic keratosis is represented by the histolopathologic analysis of a skin biopsy.
No treatment of seborrheic keratoses is necessary, except for esthetic reasons. Since a slightly increased risk of localized infection caused by picking at the lesion has been described, if a lesion becomes itchy or irritated by clothing or jewelry, a surgical excision is generally recommended.
Small lesions can be treated with light electrocautery. Larger lesions can be treated with electrodesiccation and curettage, shave excision, or cryosurgery. When correctly performed, removal of seborrheic keratoses will not cause much visible scarring except in persons with dark skin tones. Also, cryotherapy is a technique based on freezing the seborrheic keratosis growths with liquid nitrogen.
- Hafner, C; Vogt, T (Aug 2008). "Seborrheic keratosis". Journal der Deutschen Dermatologischen Gesellschaft 6 (8): 664–77. doi:10.1111/j.1610-0387.2008.06788.x. PMID 18801147.
- Freedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. ISBN 0-07-138076-0.
- James, William D.; Berger, Timothy G.; et al. (2006). Andrews' Diseases of the Skin: Clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0.
- Moles, Freckles, Skin Tags, Benign Lentigines, and Seborrheic Keratoses from the Cleveland Clinic website
- Seborrheic keratosis: Symptoms, from the Mayo Clinic website
- Fusco N, Lopez G, Gianelli U (Sep 2015). "Basal Cell Carcinoma and Seborrheic Keratosis: When Opposites Attract". Int J Surg Pathol 23 (6): 464. doi:10.1177/1066896915593802. PMID 26135529.
- Stucco Keratosis at eMedicine
- Dermatosis Papulosa Nigra at eMedicine
- Busam, Klaus J. (2010). Dermatopathology. Saunders. p. 341. ISBN 978-0-443-06654-2.
- Yeatman JM, Kilkenny M, Marks R (Sep 1997). "The prevalence of seborrhoeic keratoses in an Australian population: does exposure to sunlight play a part in their frequency?". Br J Dermatol 137 (3): 411–4. doi:10.1111/j.1365-2133.1997.tb03748.x.
- Gill D, Dorevitch A, Marks R (Jun 2000). "The prevalence of seborrheic keratoses in people aged 15 to 30 years: is the term senile keratosis redundant?". Arch Dermatol 136 (6): 759–62. doi:10.1001/archderm.136.6.759.
- Seborrheic keratosis: Causes, from the Mayo Clinic website
- Hafner C, Hartmann A, Vogt T (2007). "FGFR3 mutations in epidermal nevi and seborrheic keratoses: lessons from urothelium and skin". J. Invest. Dermatol. 127 (7): 1572–3. doi:10.1038/sj.jid.5700772. PMID 17568799.
- Seborrheic, from Merriam-Webster's online medical dictionary
- Suffix "-osis" from the Merriam-Webster website
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