3. Keratoacanthoma

Keratoacanthoma

This PatientPlus article is written for healthcare professionals so the language may be more technical than the condition leaflets. You may find the abbreviations list helpful.

Keratoacanthoma is a relatively common low-grade malignancy that originates in the pilosebaceous glands. It clinically and pathologically resembles squamous cell carcinoma (SCC).[1] 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.[1]

  • 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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Risk factors

  • Sunlight and chemical carcinogens have been implicated.
  • Trauma, genetic factors and immunocompromised status have also been associated.[3]
  • 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.



KERATOCANTHOMA - NOTE CENTRAL KERATIN PLUG



  • 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.[4][5]
  • Complete excision is the treatment of choice for all skin neoplasms thought to be keratoacanthoma.[6]
  • 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.

Radiotherapy

  • 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.
  • 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.[7]
  • Patient education in sun-protection techniques
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Further reading & references

  1. Schwartz RA; Keratoacanthoma: a clinico-pathologic enigma. Dermatol Surg. 2004 Feb;30(2 Pt 2):326-33; discussion 333.
  2. Chuang Tsu-Yi; Keratoacanthoma; eMedicine, March 2009.
  3. 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.
  4. 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.
  5. Muir-Torre Syndrome, Online Mendelian Inheritance in Man (OMIM)
  6. Manstein CH, Frauenhoffer CJ, Besden JE; Keratoacanthoma: is it a real entity? Ann Plast Surg. 1998 May;40(5):469-72.
  7. 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:
Last Checked: 22/06/2011 Document ID: 2977  Version: 22 © EMIS

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

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