Squamous cell carcinoma forms on the outermost layer of the skin. Certain precancerous growths resulting from cumulative sun damage are associated with the potential development of squamous cell carcinoma.
For example, actinic keratosis, or AK, is characterized by a rough, scaly, slightly raised growth that ranges in color from brown to red and is about one millimeter to one inch in diameter. It’s found on sun-damaged areas of the body, most often in older people, and can be the first step to squamous cell carcinoma. Some experts consider AK to be the earliest form of squamous cell carcinoma. AK is also known as solar keratosis.
Actinic cheilitis is a form of actinic keratosis that most often occurs on the lower lip and causes it to become dry, cracked, scaly and pale or white. If not treated right away, actinic cheilitis can lead to squamous cell carcinoma on the lip.
Leukoplakia begins in the mucous membranes, the white areas on the tongue, gums, cheeks or elsewhere inside the mouth. It also has the potential to develop into squamous cell carcinoma. Leukoplakia may be caused by sources of chronic irritation, such as habitual alcohol consumption or tobacco use, or rough edges on teeth or dentures. It may even be caused by a long-term habit of biting the inside of the lip. However, leukoplakia directly on the lips is usually caused by sun damage.
Bowen’s disease is generally considered an early, non-invasive stage of squamous cell carcinoma. It appears as a persistent red-brown, scaly patch that may look like eczema or psoriasis. If untreated, it can invade deeper tissue. Bowen’s disease is most often caused by sun or arsenic exposure, though other toxic chemicals, radiation, genetics and trauma may play roles as well.
The human Papillomavirus, or HPV, which can be transmitted through sexual contact, has been documented to cause one form of Bowen’s disease that affects the genitals. It can also develop in the mucous membranes of the nose and mouth, as well as on the skin. In 2006, the FDA approved an HPV vaccine that’s considered highly effective in preventing HPV and reduces the risks of genital warts and cervical cancer, as well as Bowen’s disease.
Another precancerous skin condition is keratoacanthoma, a growth that can be found on sun-exposed skin. Although it may grow quickly at first, its growth usually slows down. Keratoacanthoma may shrink or even go away on its own, over time, without any treatment. However it may continue to grow and eventually spread to other parts of the body. Many skin specialists actually consider keratoacanthoma a type of squamous cell skin cancer, rather than a precancer.