There are three forms of skin cancer: basal cell carcinoma, squamous cell carcinoma and melanoma. Skin cancer is an abnormal growth of a group of cells in the surface of the skin. Those cells can be basal cells, which is the most common form of skin cancer. When caught early and treated well, basal cell skin cancer is very curable.

Squamous cell carcinoma is the second most common type of skin cancer. Generally, this type of skin cancer is very curable. Only rarely will squamous cell carcinoma spread to other parts of the body, usually if it is neglected for a long time.

The third form of cancer - melanoma - originates in melanocytes, the cells that produce the pigment melanin that colors out skin, hair and eyes. Those cells develop into melanomas when too much sun exposure is applied to them. Melanoma is the most serious of the skin cancers. Fortunately, it is curable if caught early.

Melanoma occurs when melanocytes, the cells that make pigment, become malignant. When melanoma starts in the skin, the condition is called cutaneous melanoma. Melanoma also may occur in the eye, which is called ocular melanoma or intraocular melanoma. Rarely, melanoma can occur in the meninges, digestive tract, lymph nodes or other areas where melanocytes are found.

When melanoma spreads, cancer cells may show up in nearby lymph nodes. If the cancer has reached the lymph nodes, it may mean that cancer cells have spread to other parts of the body such as the liver, lungs or brain. In such cases, the cancer cells in the new tumor are still melanoma cells, and the condition is called metastatic melanoma, not liver, lung or brain cancer.

• Dysplastic nevi, which are more likely than ordinary moles to become cancerous. Dysplastic nevi are common, and many people have a few of these abnormal moles. The risk of melanoma is greatest for people who have a large number of dysplastic nevi. The risk is especially high for people with a family history of both dysplastic nevi and melanoma.
• Many (more than 50) normal moles: Having many moles increases the risk of developing melanoma.
• Fair skin: Melanoma occurs more frequently in people who have fair skin that burns or freckles easily than in people with dark skin. Those at risk usually have red or blond hair and blue eyes.
• Personal history of melanoma or skin cancer: People who have been treated for melanoma, basal cell carcinoma or squamous cell carcinoma are at increased risk of getting melanoma.
• Family history of melanoma: Melanoma can be hereditary. Having two or more close relatives who have had this disease is a risk factor. About 10 percent of all patients with melanoma have a family member with this disease.
• Weakened immune system: People whose immune system is weakened by certain cancers, HIV or drugs given following organ transplantation are at increased risk of developing melanoma.
• Severe, blistering sunburns: People who have had at least one severe, blistering sunburn as a child or teenager are at increased risk of melanoma. Sunburns in adulthood are also a risk factor for melanoma.
• Ultraviolet (UV) radiation: Experts believe that much of the worldwide increase in melanoma is related to an increase in the amount of time people spend in the sun. UV radiation from the sun causes premature aging of the skin and skin damage that can lead to melanoma. Artificial sources of UV radiation, such as sunlamps and tanning beds, also can cause skin damage and increase the risk of melanoma. While research has shown these are risk factors, many people who do get melanoma have no known risk factors.

The four most common and most significant signs of change are a mole or skin area that:

• Changes in size
• Changes in color---typically gets lighter and/or darker
• Itches
• Bleeds

Most melanomas have a black or blue-black area. Melanoma also may appear as a new mole. It may be black, abnormal or "ugly." Melanomas can arise in a mole that has been present for your entire life, or can start in as a new mole or dark pigmented area on the skin. In more advanced melanoma, the texture of the mole may change. For example, it may become hard or swollen. Melanomas may feel different from regular moles. More advanced tumors may itch, ooze or bleed. However, melanomas usually do not cause pain.

Remembering your "ABCDEs" can help you remember what to watch for:

• Aysmmetry -- The shape of one half does not match the other.
• Border-The edges are often jagged, uneven, distorted or atypical in outline; the pigment may spread into the surrounding skin.
• Color-The color is uneven. Shades of black, brown, and tan may be present. Areas of white, gray, red, pink or blue also may be seen.
• Diameter-There is a change in size, usually an increase. Melanomas are usually larger than the eraser of a pencil (1/4 inch or 5 millimeters).
• Evolution-anything that changes over time.

Melanomas can vary greatly in how they look. Be aware of any mole or abnormality of the skin that does not heal over time. We see more and more patients with melanomas that present in atypical ways. Often, patients report a red, raised area that looked like a "pimple" or "cyst" that just does not heal over time and gets worse. Although this is not the typical presentation of melanoma, this certainly can happen.

If you have a question or concern about something on your skin, see your physician.

Coupled with a yearly skin exam by a doctor, it is important to perform self-examinations of your skin every three months to detect the early warning signs of skin cancer.