Dermatoscope image of a keratoacanthoma with looped blood vessels. A keratoacanthoma lesion consists of a localised proliferation of squamous cells that forms a cratered nodule. The nodule grows over several weeks before gradually disappearing. However, the unsightly nodule is often surgically removed as it is clinically indistinguishable from a squamous cell carcinoma (SCC). The cause of keratoacanthoma is unknown, although exposure to sunlight appears to be a factor.