PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
Synonyms: seborrhoeic keratosis, basal cell papilloma
These are ubiquitous, benign, hyperkeratotic skin lesions associated with ageing.
This is not understood fully. Some cases of multiple seborrhoeic warts are inherited in an autosomal dominant pattern. Sunlight appears to play a role in causation, given the typical distribution of keratoses. Human papillomavirus (HPV) infection has also been implicated.
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- Presence and frequency increases with age: almost all elderly patients have some. An Australian study found that 100% of those aged over 50 in their sample had at least one seborrhoeic wart (median number of 23 warts in the 51- to 75-year range and 69 in those aged over 75).
- Onset is usually in middle age although it is a common finding in younger patients - it is found in 12% of those aged 15-25, making the term 'senile keratosis' redundant.
- No sex difference exists.
- It is less common in dark-skinned races.
- A flat-topped or warty-looking lesion that appears to be 'stuck on' to the skin.
- They are usually pigmented, sometimes deeply and may even be black. Others can be paler in colour.
- The surface is usually pitted and irregular with visible keratin dots giving a granular and rough appearance.
- They tend to have a well-circumscribed border.
Images of seborrhoeic warts
Less common variants of seborrhoeic keratoses include:
- Stucco keratoses - multiple skin-coloured or white, dry, scaly lesions often seen on the extremities (dorsa of hands, forearms, ankles and feet).
- Dermatosis papulosa nigra - multiple small, brown or black pedunculated lesions seen on the face of dark-skinned individuals. Often have an earlier onset than typical seborrhoeic keratoses.
- Melanoacanthoma - very deeply pigmented seborrhoeic keratoses.
- They start as a hyperpigmented macule and progress to the characteristic plaque.
- They start small (2 mm) and grow in size, up to 3 cm in diameter. Rarely, they can become very large.
- Initially, lesions are velvety and soft in texture, before developing a warty surface and becoming uneven, with multiple plugged follicles.
- The surface may become covered by adherent greasy scale.
- The trunk is the most common site for seborrhoeic keratoses but they are also found on all sun-exposed areas (extremities, face and scalp).
- Multiple lesions may align along skin folds.
- They are usually asymptomatic but may become irritated, itchy or inflamed spontaneously or after minor trauma.
- Malignant melanoma
- Verruca vulgaris
- Condyloma acuminatum
- Fibroepithelial polyp
- Epidermal naevus
- Melanocytic naevus
- Pigmented basal cell carcinoma
- Squamous cell carcinoma
Although skin malignancy is thought to occur by chance in patients with seborrheic warts, studies report the occasional association with Bowen's disease and squamous epithelial dysplasia. This occurs more frequently in regions with high solar ultraviolet levels. Rarely, a sudden onset or increase in the number of seborrhoeic keratoses can herald an underlying malignancy (usually adenocarcinoma of the stomach but also colon, breast and lung). It can be associated with acanthosis nigricans. This is known as the Leser-Trélat sign. The same phenomenon without internal malignancy is known as a pseudo-Leser-Trélat sign.
Primary care management
- Reassurance: most often, no treatment is required.
- Remove where there is cosmetic dislike, repeated irritation or chafing from clothes, or diagnostic uncertainty.
- Removal by cryotherapy (this may require repeat treatments), curettage and cautery or shave excision are effective and produce a better result than excision and suture, although a pale white scar can be left.
- Dermoscopy may be used by appropriately trained GPs to assist in diagnosis.
When to refer
Usually, they can be managed in primary care. However, patients with lesions requiring removal from difficult areas should be referred. Lesions that are suspicious of melanoma (either with the naked eye or by dermoscopy) should be sent as a cancer network two-week referral (TWR) to a dermatologist.
- Repeated irritation and inflammation where lesions catch on clothing.
- Aesthetic dislike.
- Concerns regarding malignancy:
- It is harder to notice a malignant melanoma arise amongst multiple seborrhoeic keratoses.
- Rarely, melanoma in situ can arise within a seborrheic keratosis, although this is rare.
Although seborrhoeic keratoses are benign, they do not spontaneously resolve and become larger and thicker with time.
Further reading & references
- Weng H, Deng Y, Xie Y, et al; Expression and significance of HMGB1, TLR4 and NF-kappaB p65 in human epidermal tumors. BMC Cancer. 2013 Jun 26;13:311. doi: 10.1186/1471-2407-13-311.
- Seborrhoeic Keratoses; DermNet NZ
- Noiles K, Vender R; Are all seborrheic keratoses benign? Review of the typical lesion and its variants. J Cutan Med Surg. 2008 Sep-Oct;12(5):203-10.
- Seborrheic Keratosis; Online Mendelian Inheritance in Man (OMIM)
- Rajabi P, Adibi N, Nematollahi P, et al; Bowenoid transformation in seborrheic keratosis: A retrospective analysis of 429 patients. J Res Med Sci. 2012 Mar;17(3):217-21.
- Yeatman JM, Kilkenny M, Marks R; The prevalence of seborrhoeic keratoses in an Australian population: does exposure to sunlight play a part in their frequency? Br J Dermatol. 1997 Sep;137(3):411-4.
- Gill D, Dorevitch A, Marks R; The prevalence of seborrheic keratoses in people aged 15 to 30 years: is the term senile keratosis redundant? Arch Dermatol. 2000 Jun;136(6):759-62.
- Stucco Keratoses; Dermnet.com, 2011 (photograph)
- Dermatitis papulosa nigra; Dermnet.com, 2011 (photograph)
- Vasani RJ, Khatu SS; Melanoacanthoma: Uncommon presentation of an uncommon condition. Indian Dermatol Online J. 2013 Apr;4(2):119-21. doi: 10.4103/2229-5178.110638.
- Seborrheic Keratosis; DermIS (Dermatology Information System)
- Gaffney DC, Muir JB, De'ambrosis B; Malignant change in seborrhoeic keratoses in a region with high solar ultraviolet levels. Australas J Dermatol. 2013 Apr 10. doi: 10.1111/ajd.12035.
- Ponti G, Luppi G, Losi L, et al; Leser-Trelat syndrome in patients affected by six multiple metachronous primitive J Hematol Oncol. 2010 Jan 11;3:2.
- Husain Z, Ho JK, Hantash BM; Sign and pseudo-sign of Leser-Trelat: case reports and a review of the literature. J Drugs Dermatol. 2013 May;12(5):e79-87.
- Luba MC, Bangs SA, Mohler AM, et al; Common benign skin tumors. Am Fam Physician. 2003 Feb 15;67(4):729-38.
- The purpose of dermoscopy in Primary Care; Primary Care Dermatology Society, 2013
- Seborrhoeic keratosis; Primary Care Dermatology Society, 2013 (good resource for images)
- Repertinger S, Wang J, Adickes E, et al; Melanoma in-situ arising in seborrheic keratosis: a case report. Cases J. 2008 Oct 23;1(1):263.
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Dr Chloe Borton
Dr Laurence Knott
Prof Cathy Jackson