Skin Cancer Foundation

Actinic Keratosis and Other Precancers

What is a Precancer?

A number of abnormal but relatively harmless skin growths may be precursors of skin cancer. These may be precancerous lesions, benign tumors that mask or mimic more serious ones or malignant tumors that are at the moment just on the topmost layer of the skin. They are important to recognize, because they are a warning sign of potential skin cancer.

Precancerous Growths

The term "precancerous" is used because these abnormal areas of skin are more likely to turn malignant than healthy skin. Precancerous growths (lesions) are visible to the naked eye, and they look different from normal cells when examined under a microscope.

What is Early Cancer?

When malignant changes occur to the skin, but haven't spread below the top layer of the skin (epidermis), they are called early cancers, or cancers in situ.

Types of Precancers

Actinic Keratosis

Actinic keratosis (AK), also known as solar keratosis, by far the most common precancer, is the result of prolonged exposure to sunlight. It is a small crusty or scaly bump or horn that arises on or beneath the skin surface. The base may be light or dark, tan, pink, red, or a combination of these ... or the same color as your skin. The scale or crust is horny, dry and rough, and is often recognized by touch rather than sight. Occasionally it itches or produces a pricking or tender sensation. It can also become inflamed and surrounded by redness. In rare instances, actinic keratoses can bleed.

The skin abnormality or lesion develops slowly and usually reaches a size from an eighth to a quarter of an inch (2mm to 4mm) but can sometimes be as large as one inch. Early on, it may disappear only to reappear later. It is not unusual to see several actinic keratoses at a time. Actinic keratoses are most likely to appear on the face, lips, ears, scalp, neck, backs of the hands and forearms, shoulders and back — the parts of the body most often exposed to sunshine. The growths may be flat and pink or raised and rough.

Actinic keratoses can be the first step leading to squamous cell carcinoma (SCC). Some studies show that ten percent do advance, and 40-60 percent of SCCS begin as untreated actinic keratoses.

Actinic cheilitis
Actinic cheilitis is a type of actinic keratosis or leukoplakia 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.

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 squamous cell carcinoma. It is caused by sources of continuous irritation, including smoking or other tobacco use, rough edges on teeth, dentures or fillings. Leukoplakia on the lips is caused mainly by sun damage.

Bowen's Disease
This is generally considered to be a superficial squamous cell carcinoma 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.

Arsenical keratosis
Far 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 lives exposed to arsenic, either contained in medication or from an industrial or environmental source.

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 squamous cell carcinoma. Often, all that is needed is a simple surgical procedure or application of a topical chemotherapeutic agent.