Keratoacanthoma ( KA) is a common low-grade (unlikely to metastasize or invade) rapidly-growing skin tumour that is believed to originate from the hair follicle (pilosebaceous unit) and can resemble squamous cell carcinoma.
The defining characteristic of a keratoacanthoma is that it is dome-shaped, symmetrical, surrounded by a smooth wall of inflamed skin, and capped with keratin scales and debris. It grows rapidly, reaching a large size within days or weeks, and if untreated for months will almost always starve itself of nourishment, necrosis (die), slough, and heal with scarring. Keratoacanthoma is commonly found on sun-exposed skin, often face, forearms and hands.[Schwartz RA. The Keratoacanthoma: A Review. J Surg Oncol 1979; 12:305–17.] It is rarely found at a mucocutaneous junction or on .
Keratoacanthoma may be difficult to distinguish visually from a skin cancer.[Ko CJ, Keratoacanthoma: facts and controversies. Clin Dermatol. 2010; 28(3):254–61 ()][Kossard S; Tan KB; Choy C; Keratoacanthoma and infundibulocystic squamous cell carcinoma. Am J Dermatopathol. 2008; 30(2):127–34 ()][Weedon DD, et al. Squamous cell carcinoma arising in keratoacanthoma: a neglected phenomenon in the elderly. Am J Dermatopathol. 2010; 32(5):423–6]
Classification
Frequently reported and reclassified over the last century, keratoacanthoma can be divided into various subtypes and despite being considered benign, their unpredictable behaviour has warranted the same attention as with squamous cell carcinoma.
Keratoacanthomas may be divided into the following types:[Freedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. .][James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology. (10th ed.). Saunders. .]
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Giant keratoacanthomas are a variant of keratoacanthoma, which may reach dimensions of several centimeters.
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Keratoacanthoma centrifugum marginatum is a cutaneous condition, a variant of keratoacanthomas, which is characterized by multiple tumors growing in a localized area.
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Multiple keratoacanthomas (also known as "Ferguson–Smith syndrome," "Ferguson-Smith type of multiple self-healing keratoacanthomas,") is a cutaneous condition, a variant of keratoacanthomas, which is characterized by the appearance of multiple, sometimes hundreds of keratoacanthomas.
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A solitary keratoacanthoma (also known as "Subungual keratoacanthoma") is a benign, but rapidly growing, locally aggressive tumor which sometimes occur in the nail apparatus.
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Generalized eruptive keratoacanthoma (also known as "Generalized eruptive keratoacanthoma of Grzybowski") is a cutaneous condition, a variant of keratoacanthomas, characterized by hundreds to thousands of tiny follicular keratotic over the entire body.
[ Treatments are not successful for many people with generalized eruptive keratoacanthoma. Use of emollients and anti-itch medications can ease some symptoms. Improvement or complete resolutions of the condition has occurred with the application of the following medications: acitretin, isotretinoin, fluorouracil, methotrexate, cyclophosphamide.]
Cause
Keratoacanthomas usually occurs in older individuals. A number of causes have been suggested including ultraviolet light, chemical
, recent injury to the skin, immunosuppression and genetic predisposition.
As with squamous cell cancer, sporadic cases have been found co-infected with the human papilloma virus (HPV).
[Niebuhr M, et al. Giant keratoacanthoma in an immunocompetent patient with detection of HPV 11. Hautarzt. 2009; 60(3):229–32 ()] Although HPV has been suggested as a causal factor, it is unproven.
Many new treatments for melanoma are also known to increase the rate of keratoacanthoma, such as the BRAF inhibitor medications vemurafenib and dabrafenib.
Diagnosis
Keratoacanthomas presents as a fleshy, elevated and nodular lesion with an irregular crater shape and a characteristic central hyperkeratotic core. Usually the people will notice a rapidly growing dome-shaped tumor on sun-exposed skin.
If the entire lesion is removed, the pathologist will probably be able to differentiate between keratoacanthoma and squamous cell carcinoma. Follow-up would be required to monitor for recurrence of disease.
Treatment
Excision of the entire lesion, with adequate margin, will remove the lesion, allow full tissue diagnosis, and leave a planned surgical wound which can usually be repaired with a good cosmetic result. However, removing the entire lesion (especially on the face) may present difficult problems of plastic reconstruction. (On the nose and face, Mohs surgery may allow for good margin control with minimal tissue removal, but many insurance companies require the definitive diagnosis of a malignancy before they are prepared to pay the extra costs of Mohs surgery.) Especially in more cosmetically sensitive areas, and where the clinical diagnosis is reasonably certain, alternatives to surgery may include no treatment (awaiting spontaneous resolution).[Keratoacanthoma. Désirée Ratner. 2004. http://www.medscape.com/viewarticle/467069 accessed 23 June 2015]
On the trunk, arms, and legs, electrodesiccation and curettage often suffice to control keratoacanthomas until they regress. Other modalities of treatment include cryosurgery and radiotherapy; intralesional injection of methotrexate or 5-fluorouracil have also been used.
Recurrence after electrodesiccation and curettage can occur; it can usually be identified and treated promptly with either further curettage or surgical excision.
History
In 1889, Sir Jonathan Hutchinson described a crateriform ulcer on the face".[
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See also
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List of skin conditions
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Marian Grzybowski
External links
