What Is Skin Cancer?

Skin cancer is the uncontrolled growth of abnormal skin cells. It occurs when damage to skin cells—most often caused by ultraviolet radiation from sunshine or tanning beds—causes skin cells to multiply rapidly and form malignant tumors. If left untreated, cancerous tumors can spread to other parts of the body including vital organs. While skin cancer is the most common form of cancer, it is also the easiest of all cancers to cure, but it must be diagnosed and treated early.