Ineffectiveness of radiotherapy for the treatment of keratoacanthoma centrifugum marginatum: A case report.

Keratoacanthoma centrifugum marginatum (KCM) is a rare variant of keratoacantoma (KA). Although KCM shares histological and clinical features with KA, KCM has no tendency of spontaneous regression, and presents with progressive peripheral expansion with a bank-shaped outer wall and concurrent central healing. As such, early diagnosis and proper treatment of the patient are required. However, because of its rarity, previous reports are insufficient to evaluate which treatment should be selected. Here, we report a case of KCM that responded to radiotherapy, but relapsed 6 months later.