Doctor using a blade to remove a keratoacanthoma on the neck of a female patient. 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. For images showing the removal of this keratoacanthoma see C059/9210 - C059/9213.