Skin cancer is the most common of all cancers, with doctors finding skin cancer in about one million Americans each year. Reducing exposure to ultraviolet (UV) radiation from sunlight can prevent most skin cancers. If skin cancer is found early, it can usually be cured by relatively simple surgery. Skin cancer is responsible for less than 1% of all cancer deaths.

The skin, the body's largest organ, protects against infection and injury and helps regulate body temperature. The skin also stores water and fat and produces vitamin D. Skin is made up of two main layers: the epidermis (outer layer of skin) and the dermis (inner layer of skin).

Types of skin cancer

Cancer begins when normal cells change and grow uncontrollably, forming a mass called a tumor. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body). There are three main types of skin cancer:

Squamous cell carcinoma. Most of the epidermis is made up of flat, scale-like cells called squamous cells. Approximately 20% of skin cancer resembles these cells and is called squamous cell carcinoma. This type of cancer is mainly caused by sun exposure, but it can appear on skin that has been burned, damaged by chemicals, or exposed to x-rays.

Basal cell carcinoma. Cells in the lower epidermis are round cells known as basal cells. About 80% of skin cancer develops from this type of cell that has been exposed to the sun and is called basal cell carcinoma. Basal cell carcinoma most often forms on the head and neck.

Melanoma. Where the epidermis meets the dermis, there are scattered cells called melanocytes, which produce the melanin that gives skin color. Melanoma starts in melanocytes, and it is the most aggressive of the three types of skin cancer. Learn more about melanoma [2]. The rest of this section describes basal cell and squamous cell skin cancers.

Squamous cell carcinoma and basal cell carcinoma are known as non-melanoma skin cancers, to distinguish them from melanoma, which arises from very different cells and is treated differently.

Typically, non-melanoma skin cancer can be treated with relatively simple surgery. If the cancer is very small, cryosurgery (freezing) or laser surgery may be used. Learn more in the Treatment [3] section. Basal cell carcinoma grows slowly and rarely metastasizes (spreads) to other parts of the body. Squamous cell carcinoma also rarely spreads, but it is more likely to spread than basal cell carcinoma.

Find out more about basic cancer terms used in this section [4].

Looking for More of an Overview?

If you would like additional introductory information, explore the following item on Cancer.Net:

• ASCO Answers Fact Sheet [5]: Read a one-page fact sheet (available in PDF) that offers an easy-to-print introduction for this type of cancer.

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