What is Skin Cancer?

What is skin cancer?

Skin cancer is the uncontrolled growth of abnormal skin cells. Skin cancer occurs when unrepaired DNA damage to skin cells triggers mutations, or genetic defects, that lead the skin cells to multiply rapidly and form malignant tumors. It is most often caused by ultraviolet radiation from sunshine or tanning beds.

Skin cancer is the most common cancer in the United States. There are two major types of skin cancer — keratinocyte cancers (basal and squamous cell skin cancers) and melanoma.

Basal cell and squamous cell cancers are the most common cancers of the skin. Both are found mainly on parts of the body exposed to the sun, such as the head and neck. These cancers are strongly related to the amount of sun exposure a person has had. Basal and squamous cell cancers are less likely than melanomas to spread to other parts of the body and become life threatening. However, if left untreated, they can grow larger and invade nearby tissues and organs, causing scarring, deformity, or even loss of function in some parts of the body.


Melanomas are cancers that develop from melanocytes, the cells that make the brown pigment that gives skin its color. Melanocytes can also form benign (non-cancerous) growths called moles. Melanomas can occur anywhere on the body, but are more likely to start in certain locations. The chest and back are the most common sites in men. In women, the legs, neck, and face are other common places for melanoma to start. Most cases of melanoma are caused by exposure to ultraviolet (UV) light.

Melanomas are not as common as basal cell and squamous cell skin cancers, but they can be far more serious. Like basal cell and squamous cell cancers, melanoma is almost always curable in its early stages. However, if left alone, melanoma is much more likely to spread to other parts of the body, where it can be very hard to treat.

It is possible to find skin cancer early because this cancer is visible. The first sign may be a slowly growing bump, a changing mole, or a dry and scaly rough patch. When treated before it spreads, most skin cancers can be cured. The key to finding skin cancer early is to know your skin. If you notice a spot or lump that is growing, bleeding, or changing, you should make an appointment to see a dermatologist.