Introduction
Background
Keratoacanthoma (KA) is a relatively common low-grade malignancy that originates in the pilosebaceous glands and closely and pathologically resembles squamous cell carcinoma (SCC). In fact, strong arguments support classifying keratoacanthoma as a variant of invasive SCC.1 Keratoacanthoma is characterized by rapid growth over a few weeks to months, followed by spontaneous resolution over 4-6 months in most cases. Keratoacanthoma reportedly progresses, although rarely, to invasive or metastatic carcinoma; therefore, aggressive surgical treatment often is advocated. Whether these cases were SCC or keratoacanthoma, the reports highlight the difficulty of distinctly classifying individual cases.2
Pathophysiology
Both sunlight and chemical carcinogens have been implicated as pathologic factors in growth of the tumor. Trauma, human papilloma virus, genetic factors, and immunocompromised status also have been implicated as etiologic factors.
Frequency
United States
The sole published study in a white US population took place in Hawaii and estimated the incidence at 104 cases per 100,000. This study reported keratoacanthoma incidence equal to SCC and challenged the commonly reported incidence ratio of keratoacanthoma to SCC of 1:3. Peak incidence occurs in the seventh decade or beyond. Keratoacanthoma is uncommon in darker-skinned patients.3,4,5,6
International
Based on the Hawaiian data, the incidence of keratoacanthoma in ethnic Japanese, Filipino, and Hawaiian populations has been estimated to be 22, 7, and 6 per 100,000, respectively, approximately one fifth to one sixteenth of the incidence rate found in American whites. In other studies, the ratio of keratoacanthoma to SCC has ranged from 1:0.6 to 1:5 in different geographic locations.3,4,5,6
Mortality/Morbidity
Keratoacanthoma is believed to have a good prognosis; however, it has been reclassified as SCC-KA type to reflect the difficulty in histologic differentiation, as well as the uncommon but potentially aggressive nature of keratoacanthoma. Keratoacanthoma infrequently presents as multiple tumors and may enlarge (5-15 cm), become aggressive locally, or rarely, metastasize.7,8
Race
Keratoacanthoma is less common in darker-skinned individuals.
Sex
Male-to-female ratio is 2:1.
Age
Keratoacanthoma has been reported in all age groups, but incidence increases with age. Keratoacanthoma is rare in persons younger than 20 years.
Clinical
History
Keratoacanthoma typically grows rapidly, attaining 1-2 cm within weeks, followed by a slow involution period lasting up to 1 year and leaving a residual scar if not excised preemptively. Since expedient therapy almost always is instituted, the true natural course of the tumor cannot be confirmed with certainty.
Physical
Pertinent physical findings are limited to the skin. Lesions typically are solitary and begin as firm, roundish, skin-colored or reddish papules that rapidly progress to dome-shaped nodules with a smooth shiny surface and a central crateriform ulceration or keratin plug that may project like a horn. Most keratoacanthomas occur on sun-exposed areas. The face, neck, and dorsum of the upper extremities are common sites. Truncal lesions are rare. Lesions usually are skin-colored to pinkish-red. Unaffected skin retains its normal appearance.
Keratoacanthoma (squamous cell carcinoma-keratoacanthoma or SCC-KA type) on inner canthus.
Keratoacanthoma of the left forehead.
Close-up view of the keratoacanthoma lesion seen in Media File 2.
Keratoacanthoma lesion (squamous cell carcinoma-keratoacanthoma or SCC-KA type).
Causes
The definitive cause of keratoacanthoma remains unclear; however, several potentiating factors should be considered. Epidemiologic data of keratoacanthoma is notably similar to SCC and Bowen disease (SCC in situ) concerning age, sex, and the anatomic site of lesions. These data strongly support a common etiology among keratoacanthoma, SCC, and Bowen disease. Epidemiologic data support sunlight as an important etiologic factor.
Industrial workers exposed to pitch and tar have been well established as having a higher incidence of keratoacanthoma, as well as SCC.9 Additionally, a 2006 study suggested a strong association between cigarette smoking and the development of keratoacanthoma.10
Trauma, human papilloma virus (specifically types 9, 11, 13, 16, 18, 24, 25, 33, 37, and 57),11,12 genetic factors, and immunocompromised status also have been implicated as etiologic factors. See Human Papillomavirus.
Finally, research has identified that up to one third of keratoacanthomas harbor chromosomal aberrations. Recurrent aberrations include gains on 8q, 1p, and 9q with deletions on 3p, 9p, 19p, and 19q. One other report identified a 46,XY,t(2;8)(p13;p23) chromosomal aberration.13,14
More on Keratoacanthoma |
 Overview: Keratoacanthoma |
| Differential Diagnoses & Workup: Keratoacanthoma |
| Treatment & Medication: Keratoacanthoma |
| Follow-up: Keratoacanthoma |
| Multimedia: Keratoacanthoma |
| References |
| Next Page » |
References
Manstein CH, Frauenhoffer CJ, Besden JE. Keratoacanthoma: is it a real entity?. Ann Plast Surg. May 1998;40(5):469-72. [Medline].
Schwartz RA. Keratoacanthoma. J Am Acad Dermatol. Jan 1994;30(1):1-19; quiz 20-2. [Medline].
Chuang TY, Reizner GT, Elpern DJ, Stone JL, Farmer ER. Keratoacanthoma in Kauai, Hawaii. The first documented incidence in a defined population. Arch Dermatol. Mar 1993;129(3):317-9. [Medline].
Chuang TY, Reizner GT, Elpern DJ, Stone JL, Farmer ER. Non-melanoma skin cancer and keratoacanthoma in Filipinos: an incidence report from Kauai, Hawaii. Int J Dermatol. Oct 1993;32(10):717-8. [Medline].
Reizner GT, Chuang TY, Elpern DJ, Stone JL, Farmer ER. Keratoacanthoma in Japanese Hawaiians in Kauai, Hawaii. Int J Dermatol. Dec 1995;34(12):851-3. [Medline].
Reizner GT, Chuang TY, Elpern DJ, Stone JL, Farmer ER. Basal cell carcinoma and keratoacanthoma in Hawaiians: an incidence report. J Am Acad Dermatol. Nov 1993;29(5 Pt 1):780-2. [Medline].
Frank TL, Maguire HC Jr, Greenbaum SS. Multiple painful keratoacanthomas. Int J Dermatol. Sep 1996;35(9):648-50. [Medline].
Sanders S, Busam KJ, Halpern AC, Nehal KS. Intralesional corticosteroid treatment of multiple eruptive keratoacanthomas: case report and review of a controversial therapy. Dermatol Surg. Oct 2002;28(10):954-8. [Medline].
Letzel S, Drexler H. Occupationally related tumors in tar refinery workers. J Am Acad Dermatol. Nov 1998;39(5 Pt 1):712-20. [Medline].
Miot HA, Miot LD, da Costa AL, Matsuo CY, Stolf HO, Marques ME. Association between solitary keratoacanthoma and cigarette smoking: a case-control study. Dermatol Online J. Feb 28 2006;12(2):2. [Medline].
Hsi ED, Svoboda-Newman SM, Stern RA, Nickoloff BJ, Frank TS. Detection of human papillomavirus DNA in keratoacanthomas by polymerase chain reaction. Am J Dermatopathol. Feb 1997;19(1):10-5. [Medline].
Lu S, Syrjanen SL, Havu VK, Syrjanen S. Known HPV types have no association with keratoacanthomas. Arch Dermatol Res. Mar 1996;288(3):129-32. [Medline].
Clausen OP, Beigi M, Bolund L, et al. Keratoacanthomas frequently show chromosomal aberrations as assessed by comparative genomic hybridization. J Invest Dermatol. Dec 2002;119(6):1367-72. [Medline].
Kim DK, Kim JY, Kim HT, Han KH, Shon DG. A specific chromosome aberration in a keratoacanthoma. Cancer Genet Cytogenet. Apr 1 2003;142(1):70-2. [Medline].
Meffert JJ. Cutaneous sporotrichosis presenting as a keratoacanthoma. Cutis. Jul 1998;62(1):37-9. [Medline].
Sayama S, Tagami H. Treatment of keratoacanthoma with intralesional bleomycin. Br J Dermatol. Oct 1983;109(4):449-52. [Medline].
Annest NM, VanBeek MJ, Arpey CJ, Whitaker DC. Intralesional methotrexate treatment for keratoacanthoma tumors: a retrospective study and review of the literature. J Am Acad Dermatol. Jun 2007;56(6):989-93. [Medline].
Dendorfer M, Oppel T, Wollenberg A, Prinz JC. Topical treatment with imiquimod may induce regression of facial keratoacanthoma. Eur J Dermatol. Jan-Feb 2003;13(1):80-2. [Medline].
Grob JJ, Suzini F, Richard MA, et al. Large keratoacanthomas treated with intralesional interferon alfa-2a. J Am Acad Dermatol. Aug 1993;29(2 Pt 1):237-41. [Medline].
Canas GC, Robson KJ, Arpey CJ. Persistent keratoacanthoma: challenges in management. Dermatol Surg. Dec 1998;24(12):1364-9. [Medline].
Fitzpatrick T, Eisen A, Wolff K, et al, eds. Keratoacanthoma. In: Dermatology in General Medicine. 1993. 4th ed. New York, NY: McGraw-Hill; 848-855.
Further Reading
Keywords
keratoacanthoma, KA, squamous cell carcinoma, SCC, invasive SCC, invasive squamous cell carcinoma, squamous cell cancer, skin cancer, skin malignancy, pilosebaceous gland cancer, pilosebaceous glands
