Types of precancer

Actinic cheilitisActinic cheilitis is a type of actinic keratosis occurring on the lips. It causes them to become dry, cracked, scaly and pale or white. It mainly affects the lower lip, which typically receives more sun exposure than the upper lip.
Arsenical keratosisFar less common, arsenical keratosis is an accumulation of keratinized tissue that at first resembles numerous small, yellowish corns. These arise most often on the palms, soles, and inner surfaces of the finger and toes, and then enlarge and thicken, sometimes increasing in number. Although rarely seen today, arsenical keratoses usually occur on patients who were at some time in their live exposed to arsenic, either contained in medication or from an industrial or environmental source.
Leukoplakia Leukoplakia is a disease of the mucous membrane. White patches or plaques develop on the tongue or inside of the mouth, and have the ability to develop into SCC. It is caused by sources of continuous irritation, including smoking or other tobacco use, rough teeth or rough edges on dentures and fillings. Leukoplakia on the lips are mainly caused by sun damage.
Bowen's DiseaseThis is generally considered to be a superficial SCC that has not yet spread. It appears as a persistent red–brown, scaly patch which may resemble psoriasis or eczema. If untreated, it may invade deeper structures.Regardless of appearance, any change in a preexisting skin growth, or the development of a new growth or open sore that fails to heal, should prompt an immediate visit to a physician. If it is a precursor condition, early treatment will prevent it from developing into SCC. Often, all that is needed is a simple surgical procedure or application of a topical chemotherapeutic agent.