Keratoacanthoma centrifugum marginatum.

Keratoacanthoma centrifugum marginatum (KCM) is an uncommon variant of keratoacanthoma. Keratoacanthoma centrifugum marginatums are most commonly seen on sun-exposed surfaces and present with progressive peripheral expansion and raised, hyperkeratotic borders. Central clearing with atrophy and lack of spontaneous clearance are other key clinical characteristics. The majority of cases are benign with a low risk of metastasis. The size of such growths is variable with reported cases ranging from 5.0cm×5.0cm to as large as 20.0cm×14.0cm. Treatment options include surgical excision, oral retinoids, and intralesional chemotherapeutics such as methotrexate or bleomycin. We herein present a case of KCM manifesting as an exophytic, crateriform plaque in a 61-year-old man.