Lesions (benign)

Seborrhoeic keratosis

Last Reviewed:January, 2016

What is a seborrhoeic keratosis?

Seborrhoeickeratosis is a harmlesswarty spot that appears during adult life as a commonsign ofskin ageing. Some people have hundreds of them.

Seborrhoeic keratosis (American spelling - seborrheic keratosis) is also called SK,basal cellpapilloma, senile wart, brown wart, wisdom wart, or barnacle. The descriptive term,benign keratosis, is a broader term that is used to include the following relatedscaly skinlesions:

• Seborrhoeic keratosis
• Solar lentigo (which can be difficult to distinguish from a flat seborrhoeic keratosis)
• Lichen planus-like keratosis (which arises from a seborrhoeic keratosis or a solarlentigo).

Seborrhoeic keratosis 

Seborrhoeic keratosis 

Pigmented seborrhoeic keratosis 

Who gets seborrhoeic keratoses?

Seborrhoeickeratoses are extremely common. It has been estimated that over 90% of adults over the age of 60 years have one or more of them. They occur in males and females of all races, typically beginning to erupt in the 30s or 40s. They are uncommon under the age of 20 years.

What causes seborrhoeic keratoses?

The precise cause of seborrhoeic keratoses is not known.

The name is misleading, because they are not limited to a seborrhoeicdistribution (scalp, mid-face, chest, upper back) as inseborrhoeic dermatitis, nor are they formed fromsebaceousglands, as is the case withsebaceous hyperplasia, nor are they associated withsebum — which is greasy.

Seborrhoeic keratoses are considereddegenerative in nature. As time goes by, seborrhoeic keratoses become more numerous. Some people inherit a tendency todevelop a very large number of them. Researchers have noted:

• Eruptive seborrhoeic keratoses can followsunburn ordermatitis.
• Skin friction may be the reason they appear in body folds.
• Viral cause (eg human papillomavirus) seems unlikely.
• Stable andclonalmutations or activation of FRFR3, PIK3CA, RAS, AKT1 and EGFRgenes are found in seborrhoeic keratoses.
• Seborrhoeic keratosis can arise fromsolar lentigo.
• FRFR3 mutations also arise in solarlentigines. These mutations are associated with increased age and location on the head and neck, suggesting a role ofultraviolet radiation in these lesions.
• Seborrhoeic keratoses do not harbourtumour suppressorgene mutations.
• Epidermal growth factor receptor inhibitors (used to treatcancer) often result in an increase in verrucal (warty) keratoses.

What are the clinical features of seborrhoeic keratoses?

Seborrhoeic keratoses can arise on any area of skin, covered or uncovered, with the exception of palms and soles. They do not arise frommucous membranes.

Seborrhoeic keratoses have a highly variable appearance.

• Flat or raisedpapule orplaque
• 1 mm to several cm in diameter
• Skin coloured, yellow, grey, light brown, dark brown, black or mixed colours
• Smooth, waxy or warty surface
• Solitary orgrouped in certain areas, such as within the scalp, under the breasts, over the spine or in the groin

They appear to stick on to the skin surface like barnacles.

Seborrhoeic keratosis 

Seborrhoeic keratosis 

Seborrhoeic keratosis 

• See more images of seborrhoeic keratoses
• See dermoscopy images of seborrhoeic keratoses

Variants of seborrhoeic keratoses

Variants of seborrhoeic keratoses include:

• Solar lentigo: flatcircumscribed pigmented patches in sun-exposed sites
• Dermatosis papulosa nigra: small,pedunculated and heavily pigmented seborrhoeic keratoses on head and neck of darker-skinned individuals
• Stucco keratoses: grey, white or yellowpapules on the lower extremities
• Invertedfollicular keratosis
• Large cellacanthoma
• Lichenoid keratosis: aninflammatory phase precedinginvolution of some seborrhoeic keratoses and solar lentigines.

Florid lesions of stucco keratoses on the ankle 

Dermatosis papulosa nigra 

Irritated seborrhoeic keratosis 

 

Complications of seborrhoeic keratoses

Seborrhoeic keratoses are notpremalignanttumours. However:

• Skin cancers are sometimes difficult to tell apart from seborrhoeic keratoses.
• Skin cancer may by chance arise within or collide with a seborrhoeic keratosis.

Very rarely, eruptive seborrhoeic keratoses may denote an underlying internalmalignancy, most often gastricadenocarcinoma. Theparaneoplasticsyndrome is known as thesign of Leser-Trélat. Eruptive seborrhoeic keratoses that are not associated with cancer are sometimes described as having pseudo-sign of Leser-Trélat.

Eruptive and irritated seborrhoeic keratoses may also arise as anadverse reaction to a medication, such asadalimumab,vemurafenib,dabrafenib,5-fluorouracil and manychemotherapy drugs.

An irritated seborrhoeic keratosis is an inflamed, red andcrustedlesion. It may give rise toeczematous dermatitis around the seborrhoeic keratosis.Dermatitis may also trigger new seborrhoeic keratoses to appear.

How is a seborrhoeic keratosis diagnosed?

The diagnosis of seborrhoeic keratosis is often easy.

• A stuck-on, well-demarcated warty plaque
• Other similar lesions

Sometimes, seborrhoeic keratosis may resembleskin cancer, such asbasal cell carcinoma,squamous cell carcinoma ormelanoma.

Dermoscopy often shows a disordered structure in aseborrhoeic keratosis, as is also true for skin cancer. There are diagnosticdermatoscopic clues to seborrhoeic keratosis, such as multiple orange or brownclods (due tokeratin in skin surface crevices), whitemilia-like clods, and curved thick ridges and furrows forming a brain-like or cerebriform pattern.

If doubt remains, a seborrhoeic keratosis may undergo partialshave or punch biopsy or diagnosticexcision. [seeSeborrhoeic keratosis pathology]

The dominanthistopathological features of seborrhoeic keratosis may be described as:

• Melanoacanthoma (deeply pigmented)
• Acanthotic
• Hyperkeratotic orpapillomatous
• Adenoid orreticulated
• Clonal or nested
• Adamantinoid or mucinous
• Desmoplastic
• Irritated.

What is the treatment for seborrhoeic keratoses?

An individual seborrhoeic keratosis can easily be removed if desired. Reasons for removal may be that it is unsightly, itchy, or catches on clothing.

Methods used to remove seborrhoeic keratoses include:

• Cryotherapy (liquid nitrogen) for thinner lesions (repeated if necessary)
• Curettage and/orelectrocautery
• Ablative laser surgery
• Shave biopsy (shaving off with a scalpel)
• Focalchemical peel with trichloracetic acid

All methods have disadvantages. Treatment-induced loss ofpigmentation is a particular issue for dark-skinned patients. There is no easy way to remove multiple lesions on a single occasion.

How can seborrhoeic keratoses be prevented?

How to prevent seborrhoeic keratoses is unknown.

What is the outlook for seborrhoeic keratoses?

Seborrhoeic keratoses tend topersist. From time to time, individual or multiple lesions mayremit spontaneously or via thelichenoid keratosis mechanism.

Those associated withdermatitis may regress after it has been controlled.

References

• Jackson JM, Alexis A, Berman B, Berson DS, Taylor S, Weiss JS. Current Understanding of Seborrheic Keratosis: Prevalence, Etiology, Clinical Presentation, Diagnosis, and Management. J Drugs Dermatol. 2015 Oct 1;14(10):1119–25.PubMed
• Hafner C, Hartmann A, van Oers JM, Stoehr R, Zwarthoff EC, Hofstaedter F, Landthaler M, Vogt T. FGFR3 mutations in seborrheic keratoses are already present in flat lesions and associated with age and localization. Mod Pathol. 2007 Aug;20(8):895–903. Epub 2007 Jun 22.PubMed
• Hafner C, Hafner H, Groesser L. [Genetic basis of seborrheic keratosis and epidermal nevi]. Pathologe. 2014 Sep;35(5):413–23. doi: 10.1007/s00292-014-1928-9. Review. German.PubMed
• Hida Y, Kubo Y, Arase S. Activation of fibroblast growth factor receptor 3 and oncogene-induced senescence in skin tumours. Br J Dermatol. 2009 Jun;160(6):1258–63. doi: 10.1111/j.1365-2133.2009.09068.x. Epub 2009 Mar 9.PubMed
• Husain Z, Ho JK, Hantash BM. Sign and pseudo-sign of Leser-Trélat: case reports and a review of the literature. J Drugs Dermatol. 2013 May;12(5):e79–87. Review.PubMed

On DermNet

• Skin ageing
• Solar lentigo
• Brown marks and freckles
• Benign keratinocytic and adnexal tumours – common skin lesions course
• Comedo
• Common benign skin lesions

Other websites

• Stucco Keratosis — Medscape Reference
• Seborrheic Keratosis — Medscape Reference
• Seborrhoeic Warts — British Association of Dermatologists
• Patient information: Seborrheic keratosis (The Basics) — UpToDate (for subscribers)
• Seborrheic Keratosis — American Academy of Dermatology

Books about skin diseases

• Books about the skin
• Dermatology Made Easy - second edition