MedGen

A localized pathological or traumatic structural change, damage, deformity, or discontinuity of skin. [from NCI]

A pathological process with signs indicating it may become cancerous. Representative examples include leukoplakia, dysplastic nevus, actinic keratosis, xeroderma pigmentosum, and intraepithelial neoplasia. [from NCI]

A scaly, crusty lesion caused by damage from the ultraviolet radiation of the sun, with typical location on sun-exposed areas of the skin. Actinic keratosis lesions are often elevated, rough, and wartlike, and may be red, or occasionally tan, pink, or flesh-toned in color. [from HPO]

Excessive growth of keratin on the skin. [from NCI]

Keratoacanthoma (KA) is a common benign epithelial tumor that originates from the pilosebaceous glands. In most cases, it is characterized by rapid evolution, followed by spontaneous resolution over 4 to 6 months. KA usually presents as a solitary flesh-coloured nodule with a central keratin plug on the sun-exposed skin of elderly individuals. [from HPO]

Focal or diffuse thickening of the skin not inherited as a primary genetic disorder. Causes include inflammatory skin disorders, infectious disorders, lymphedema, and medications. [from NCI]