Keratoacanthoma centrifugum marginatum: report of a rare variant of keratoacanthoma

We report a case of a 72-year-old man who underwent surgical excision of a keratoacanthoma centrifugum marginatum (KCM) located on the left forearm. It is an uncommon variant of keratoacanthoma, which can assume large dimensions (up to 20 cm) and does not tend to spontaneous regression. The lesion is usually single, with raised borders, and has progressive centrifugal growth associated with central healing and atrophy. Due to its rarity and lack of pathognomonic histopathological features, KCM can be a diagnostic challenge for dermatologists and pathologists.