Skin cancer occurs when abnormal skin cells begin to grow out of control. While normal cells divide and develop in an orderly fashion, cancer cells do not. Skin cancer cells may penetrate or invade surrounding tissue. They may also spread to other parts of the body through the blood or lymphatic systems. As cancer cells continue to grow, they crowd out normal cells and often form into a mass of tissue called a growth or tumor. These growths may inhibit normal body function by blocking up internal organs or blood vessels, or destroying nerve pathways, etc. Skin cancer (mostly melanoma) can sometimes lead to death.