Keratoacanthoma is a relatively common low-grade malignancy that originates in the pilosebaceous glands. It clinically and pathologically resembles squamous cell carcinoma (SCC). Keratoacanthoma rarely progresses into an invasive SCC. Keratoacanthoma may serve as a marker for the important autosomal dominant familial cancer syndrome, the Muir-Torre syndrome.
- Incidence is estimated at 1 in 1,000.
- Peak incidence occurs in those aged over 60 years. Is rare in young adults.
- It is uncommon in darker-skinned patients.
- Males are twice as often affected as females.
- Epidemiological data are similar to squamous cell carcinoma (SCC) and Bowen's disease in terms of age, sex and the site of lesions.
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- Sunlight and chemical carcinogens have been implicated.
- Trauma, genetic factors and immunocompromised status have also been associated.
- Industrial workers exposed to pitch and tar have a higher incidence of both keratoacanthoma and SCC.
- Typically rapid growth over a few weeks to months, followed by a slow spontaneous resolution over 4-6 months (but may take up to 1 year).
- Most occur on sun-exposed areas, eg the face, neck, and dorsum of hands and forearms.
- They are usually solitary and begin as firm, round, skin-coloured or reddish papules that rapidly progress to dome-shaped nodules with a smooth shiny surface. A central crater of ulceration may develop, or a keratin plug that may project like a horn.
- It leaves a residual scar if not excised.
- Occasionally presents as multiple tumours and may enlarge to up to 15 cm, become locally aggressive and metastasise.
- Shave biopsy of keratoacanthoma is indistinguishable from invasive squamous cell carcinoma (SCC). Therefore, excisional or deep incisional biopsy is required.
- The Muir-Torre syndrome includes the presence of sebaceous gland tumours, with or without keratoacanthomas, and associated with visceral malignancies, especially colorectal. It has autosomal dominant inheritance.
- Complete excision is the treatment of choice for all skin neoplasms thought to be keratoacanthoma.
- Medical treatment is reserved for when surgical intervention is not possible, eg multiple lesions not amenable to surgery because of size or location.
- Treatments that have produced some success include systemic retinoids (eg isotretinoin), intralesional methotrexate, 5-fluorouracil, bleomycin and steroids, and topical imiquimod and 5-fluorouracil.
- Keratoacanthomas are radiosensitive and respond well to low doses of radiation.
- Radiation therapy may be useful in selected patients with large tumours when resection will result in cosmetic deformity, or for tumours that have recurred following attempted excision.
- Both laser therapy and cryotherapy have been used successfully in small keratoacanthomas.
- Reportedly progresses, although rarely, to invasive or metastatic carcinoma.
- Prognosis is excellent following excisional surgery.
- Without surgery, prognosis is usually good but it has recently been reclassified as squamous cell carcinoma (SCC)-keratoacanthoma type to reflect the difficulty in histological differentiation, as well as the uncommon but potentially aggressive nature of keratoacanthoma.
- There is increased risk for developing subsequent nonmelanoma skin cancer.
- Patient education in sun-protection techniques
Further reading & references
- Schwartz RA; Keratoacanthoma: a clinico-pathologic enigma. Dermatol Surg. 2004 Feb;30(2 Pt 2):326-33; discussion 333.
- Chuang Tsu-Yi; Keratoacanthoma; eMedicine, March 2009.
- Clausen OP, Beigi M, Bolund L, et al; Keratoacanthomas frequently show chromosomal aberrations as assessed by comparative genomic hybridization. J Invest Dermatol. 2002 Dec;119(6):1367-72.
- Ponti G, Losi L, Di Gregorio C, et al; Identification of Muir-Torre syndrome among patients with sebaceous tumors and keratoacanthomas: role of clinical features, microsatellite instability, and immunohistochemistry. Cancer. 2005 Mar 1;103(5):1018-25.
- Muir-Torre Syndrome, Online Mendelian Inheritance in Man (OMIM)
- Manstein CH, Frauenhoffer CJ, Besden JE; Keratoacanthoma: is it a real entity? Ann Plast Surg. 1998 May;40(5):469-72.
- Graells J; The risk and risk factors of a second non-melanoma skin cancer: a study in a Mediterranean population. J Eur Acad Dermatol Venereol. 2004 Mar;18(2):142-7.
|Original Author: Dr Colin Tidy||Current Version: Dr Colin Tidy|
|Last Checked: 22/06/2011||Document ID: 2977 Version: 22||© EMIS|
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