Keratoacanthoma (KA) is a relatively common, benign, epithelial tumor that was previously consiered to be a variant of squamous cell carcinoma (SCC). The etiology is unknown. No human papillomavirus-DNA sequences were detected in lesions by polymerase chain reaction. It is a disease of the elderly (mean age, 64 years) with an annual incidence rate of 104 per 100,000. It is not associated with internal malignancy. There may be a seasonal presentation of keratoacanthoma that suggests that ultraviolet radiation has an acute effect on the development of KA. KAs may develop in sites of previous trauma. Most cases are the “crateriform” type, which grow rapidly then undergo spontaneous regression. Less than 2% belong to the rare destructive variants with no regression and persistent invasive growth. These are referred to as keratoacanthoma marginatum centrifugum and mutilating keratoacanthomas and can lead to severe defects.