A number of abnormal but relatively harmless skin growths may be precursors of skin cancer. They are important to recognize because they are a warning sign of potential skin cancer.
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. 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. Generally all that is needed is a simple surgical procedure or application of a topical chemotherapeutic agent.

Basal cell carcinoma (BCC) is the most common form of cancer. Basal cells line the deepest layer of the epidermis, and basal cell carcinomas are malignant growths that arise in this layer.
Basal cell carcinoma can usually be diagnosed with a simple biopsy and is fairly easy to treat when detected early. However, 5 to 10 percent of BCCs can be resistant to treatment or locally aggressive, damaging the skin around them and sometimes invading bone and cartilage. When not treated quickly they can be difficult to eliminate.
Fortunately, this is a cancer that has an extremely low rate of metastasis and although it can result in scars and disfigurement it is not usually life threatening.
The sun is responsible for over 90 percent of all skin cancers, including BCCs, which occur most frequently on the sun-exposed areas of the body: face, ears, neck, scalp, shoulders and back.

Squamous cell carcinoma (SCC) is the second most common form of skin cancer. It arises in the squamous cells that compose most of the upper layer of the skin. Most SCCs are not serious, but if overlooked they are harder to treat and can cause disfigurement. While 96 to 97 percent of SCCs are localized the small percentage of remaining cases can spread to distant organs and become life-threatening.
As with BCC, most cases of squamous cell carcinoma are caused by chronic overexposure to the sun. SCCs may also occur where skin has suffered certain kinds of injury: burns, scars, long-standing sores, sites previously exposed to X-rays or certain chemicals. In addition, chronic skin inflammation or medical conditions that suppress the immune system over an extended period of time may encourage development of the disease.

Melanoma is the most serious form of skin cancer. If recognized and treated early it is nearly 100 percent curable, but if not the cancer can advance to other parts of the body where it becomes hard to treat and can be fatal. While it is not the most common of the skin cancers, it causes the most deaths. The American Cancer Society estimates that in 2009, there will be 8,420 fatalities in the U.S.
Melanoma is a malignant tumor that originates in melanocytes, the cells which produce the pigment melanin that colors our skin, seborrheic dermatitis, atopic dermatitis,Irritant dermatitis,Contact dermatitis, and eyes. The majority of melanomas are black or brown, however some melanomas are pink, red, purple, blue or white.
Everyone is at risk for melanoma, however heredity plays a major role. About one of every ten patients diagnosed with the disease has a family member with a history of melanoma. If melanoma is present in your family, you can protect yourself and your children by being particularly vigilant in watching for the early warning signs and finding the cancer when it is easiest to treat.

If a mole or pigmented area of the skin changes or looks abnormal, the following tests and procedures can help detect and diagnose melanoma:

• Skin examination: A doctor or nurse examines the skin to look for moles, birthmarks, or other pigmented areas that look abnormal in color, size, shape, or texture.
• Biopsy: A local excision is done to remove as much of the suspicious mole or lesion as possible. A pathologist then looks at the tissue under a microscope to check for cancer cells.

Because melanoma can be hard to diagnose, patients should consider having their biopsy sample checked by a second pathologist. Suspicious areas should not be shaved off or cauterized.