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Keratoacanthoma (KA) is common skin tumor that arises predominantly on sun-exposed areas. Clinical manifestations of KA include solitary KA and multiple KAs, and can present in a sporadic fashion, inherited fashion, or in association with inflammatory diseases. Provoking factors include immunosuppression/immunodeficiency, electromagnetic radiation, trauma, chemical factors, drugs that influence the cell cycle, and foreign bodies. Solitary KAs are firm crateriform nodules 1 to 2 cm in diameter, with the giant variant greater than 2 to 3 cm. Multiple KAs can present as KA centrifugum marginatum (persistent peripheral growth), Ferguson-Smith type (1-100 s of noncrateriform nodules), Gryzbowski type (100 s to 1000 s of 1 to -5 mm follicular papules and larger crateriform nodules), or Witten-Zak type (1-5 mm follicular papules and larger nodules). In the authors’ experience, surgical therapy is usually initiated with solitary lesions, with injected medications usually reserved for numerous or recalcitrant cases. See Table 104-1.
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