“Actinic Keratosis a rough, scaly patches of skin that are considered precancerous and are due to sun exposure. Prevention is to cut sun exposure and wear sunscreen. Treatments include performing cryosurgery (freezing with liquid nitrogen), cutting the keratoses away, burning them, putting 5-fluorouracil on them, and using photodynamic therapy (injecting into the bloodstream a chemical that collects in actinic keratoses and makes them more sensitive to destruction by a specialized form of light).

Keratoacanthoma 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.”

Medicine Net (https://www.medicinenet.com/image-collection/actinic_keratosis_solar_keratosis_picture/picture.htm)