What is skin cancer?

There are 2 main types of skin cancers: keratinocyte cancers (basal and squamous cell skin cancers) and melanomas.

• Basal and squamous cell skin cancers are by far the most common cancers of the skin. They develop from cells called keratinocytes, the most common cells in the skin.
• 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.

There are many other types of skin cancers as well, but these are much less common.

It is important for doctors to tell these types of skin cancer apart, because they are treated differently. It is also important for you to know what melanomas and basal and squamous cell skin cancers look like. This may help you find them at the earliest possible stage, when they are cured most easily.

Basal and squamous cell cancers (keratinocyte cancers)

Basal cell cancers and squamous cell cancers are the most common cancers of the skin. They develop from skin cells called keratinocytes. Both basal cell and squamous cell cancers are found mainly on parts of the body exposed to the sun, such as the head and neck, and their occurrence is related to the amount of sun exposure a person has had.

These cancers (especially basal cell cancers) rarely spread elsewhere in the body and are much less likely than melanomas to be fatal. Still, it is important to find and treat them early. If left untreated, they can grow quite large and invade into nearby tissues, causing scarring, disfigurement, or even loss of function in some parts of the body.

These cancers are discussed in more detail in our document, Skin Cancer: Basal and Squamous Cell.

Melanomas

Melanomas can occur anywhere on the body, but are more likely to start in certain locations. The trunk (chest and back) is the most common site in men. In women, the legs are the most common site. The neck and face are other common sites.

Melanomas are much less common than 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. But if left alone, melanoma is much more likely to spread to other parts of the body, where it can be very hard to treat.

Melanomas are discussed in more detail in our document, Melanoma Skin Cancer.