Keratoacanthoma (KA) is a growth that is relatively common, benign, and most commonly found in elderly light-skinned individuals. It is more common with individuals having an increased degree of sun exposure and is often found at sites of previous injury or trauma. It is not associated with internal malignancy, except in rare instances where multiple keratoacanthomas are associated with a disease process called Muir-Torre syndrome.
KA is a rapidly growing growth on the skin that expands from 1-2mm to 1-3cm over a few weeks, and develops into a smooth dome-shaped growth with a central keratin core. If untreated, KA's usually stop growing around 6-8 weeks, stay dormant and unchanging for 2-6 weeks, and then finally spontaneously regress slowly over 2 to 12 months frequently healing with scarring. KA's are most commonly found in the hands, arms, trunk and face.
Although KA's are benign spontaneously regressing growths, treatment is indicated because KA's can not always be distinguished from squamous cell carcinomas. Also KA's ultimately heal with scarring. Treatment options include surgical excision, electrodesiccation and curettage, and multiple medical techniques. Topical 5-fluorouracil cream applied three times a day for 1 to 6 weeks has been found to be effective. Excellent results have been reported with 5-fluorouracil injections. This technique is especially useful for large rapidly growing KA's. Podophyllin resin, methotrexate intralesional injections, and radiotherapy are effective for giant KA's. Oral isotretinoin and oral acitretin have been shown to be useful in treating patients with multiple KA's.
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