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keratoacanthoma (KA)

A dome-shaped isolated nodule generally on the face with a central keratinous crater (central hyperkeratotic core). Etiology: 1) HPV types 9, 16, 19, 25 & 37 have been identified in keratoacanthomas 2) ultraviolet radiation has been suggested 3) chemical carcinogens have been proposed: pitch & tar Epidemiology: 1) generally occurs in individuals > 60 years of age (MKSAP20) [4] 2) rare in individuals < 20 years old 3) male:female ratio 2:1 4) Caucasians: rare in Asians & blacks Pathology: - rapidly growing neoplasm of squamous cells that terminally differentiate with spontaneous involution - despite spontaneous involution, the neoplasm can be quite destructive [4] - in immunosuppressed, may evolve into, if not is, squamous cell carcinoma skin (see differential diagnosis) [3] - ref [4] describes keratoacanthoma as a form of squamous cell carcinoma skin Clinical manifestations: 1) dome-shaped isolated nodule with central ulceration with keratin plug - resembles cinder cone of volcano [4] 2) tan, brown, pink or red in color (not white) [4] 3) firm, but not hard in texture 4) occurs on exposed skin, cheeks, nose, ears, dorsal aspect of hands 5) rapid growth up to 2.4 cm within a few weeks - can arise spontaneously or after local trauma [4] 6) frequently painful or tender, but may be asymptomatic [4] 7) generally NOT associated with telangiectasias or bleeding [3] 8) cosmetic disfigurement 9) spontaneous regression in 2-6 months, occasionally > 1 year * images [5,6] Differential diagnosis: 1) squamous cell carcinoma skin (SCCS) - immunosuppression increases risk of SCCS - location of temple, forehead, nose increases risk of SCCS [3] 2) basal cell carcinoma 3) hypertrophic actinic keratosis 4) verruca vulgaris - hyperkeratotic, exophytic, firm papules - may be white dome-shaped - thrombosed blood vesselscan be seen as pinpoint red-to-maroon dots on the white dome [4] * do not choose keratoacanthoma without central ulceration Complications: - some keratoacanthomas may persists or even metastasize [4] Management: 1) surgical excision a) provides tissue for histology b) removes cosmetic problem c) treat as squamous cell carcinoma 2) systemic retinoids & methotrexate have been used for multiple lesions, but are not very effective 3) topical 5-fluorouracil (5-FU) [2]

Related

papillomavirus

General

keratosis acanthoma

References

  1. Color Atlas & Synopsis of Clinical Dermatology, Common & Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY, 1997, pg 170-171
  2. Usatine R. In: Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 12-15, 2001
  3. Geriatrics Review Syllabus, American Geriatrics Society, 5th edition, 2002-2004 - Geriatric Review Syllabus, 9th edition (GRS9) Medinal-Walpole A, Pacala JT, Porter JF (eds) American Geriatrics Society, 2016 - Geriatric Review Syllabus, 11th edition (GRS11) Harper GM, Lyons WL, Potter JF (eds) American Geriatrics Society, 2022
  4. Medical Knowledge Self Assessment Program (MKSAP) 15, 16, 17, 18, 19. American College of Physicians, Philadelphia 2009, 2012, 2015, 2018, 2022. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022 - Medical Knowledge Self Assessment Program (MKSAP) 20 American College of Physicians, Philadelphia 2025
  5. Chuang TY, James WD (images) Medscape: Keratoacanthoma http://emedicine.medscape.com/article/1100471-overview
  6. DermNet NZ. Keratoacanthoma (images) http://www.dermnetnz.org/lesions/keratoacanthoma.html