Noncancerous, Precancerous and Cancerous Tumors

Keratoacanthoma on the forehead of a 77-year-old woman. This is a harmless, hard nodule that appears on the skin, most commonly on the face or arm of elderly people. The nodule may grow to up to 2 centimeters in diameter over about 8 weeks before gradually disappearing. However, the unsightly nodule is often surgically removed. The cause of keratoacanthoma is unknown, although exposure to sunlight appears to be a factor.