Skin cancer refers to the abnormal, uncontrolled growth of skin cells. The most common skin cancers are basal cell carcinoma (affecting cells in the lowest layer of the epidermis) and squamous cell carcinoma (affecting cells in the middle layer of the epidermis). A rarer but more dangerous skin cancer is melanoma, the leading cause of death from skin disease. Risk factors for developing skin cancer include pale skin, family history of melanoma, being over 40 years old, and regular sun exposure. Skin cancers vary in shape, color, size and texture, so any new, changed or otherwise suspicious growths or rashes should be examined immediately by a physician. Early intervention is essential to preventing the cancer from spreading.