Like other cancer types, skin cancer is generally caused if the cells are being exposed to an environmental condition. This makes cells, or even genes to mutate into oncogenes. An oncogene triggers tumor growth. In most cases it is unclear what environmental condition may have caused cancer. In case of skin cancer, it is thought that the environmental condition causing tumor formation is ultraviolet radiation. Sunlight is the most common ultraviolet radiation source we are usually exposed to. Some individuals are more sensitive to ultraviolet radiation than others. Excessive exposure to the sunlight will eventually lead to skin cancer for most individuals. This is based on the melanin amount present in the body. Melanin is the natural defense of the body against the sun. It makes the skin brown to protect it from burning. People who have low levels of melanin have paler skin. Pale skin will turn red and not brown and it will be burnt before it?s tanned. People with blue or pale eyes and fair hair are at higher risk of developing skin cancer. The skin cancer effects may be various. The most common skin cancer type is basal cell carcinoma. Generally it looks like a brown or red mark on the skin. It might be flat or raised from the skin. It doesn’t spread anywhere and is thought to be a benign tumor. Squamous cell carcinoma is a type of skin cancer which is often found on the body parts exposed to the sunlight. It does not spread from its original location. And if it spreads it will affect only the surrounding cells. If it?s on the skin surface you will see a red or brown mark that is getting larger over time. Melanoma is another form of skin cancer. This type is the most severe and rarest skin cancer. They appear in any area of the body, even those parts which are not usually exposed to the sun. They may appear as a brown spot which is getting larger or as a lump present under the skin. Melanoma may be malignant, which means that it will grow uncontrollably and in random. If melanoma becomes invasive, this becomes a real problem. It will interfere with the surrounding organs and tissues to such an extent that it stops them working. The best prevention you can take is to limiting the exposure to sun and other sources of ultraviolet radiation. It is nice to have your skin checked by the doctor regularly. It is good advice especially if you notice any new moles or unusual spots on the skin.