Overview

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 begin to 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 10% to 30% 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. This section describes basal cell and squamous cell skin cancers. Learn more about melanoma.

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. 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.

Statistics

In 2009, more than 1 million cases of non-melanoma skin cancer are expected to be diagnosed in the United States. Basal cell carcinoma and squamous cell carcinoma are highly curable and are not traditionally included in overall cancer statistics. An estimated, 2,940 deaths from non-melanoma skin cancer will occur this year.

Basal cell carcinoma. This is the most common type of skin cancer, accounting for about 80% of all skin cancers. Basal cell carcinoma grows slowly and does not usually spread. Nearly half of people with one basal cell carcinoma develop another one within five years.

Squamous cell carcinoma. This skin cancer makes up 20% of all skin cancers and may grow faster than a basal cell carcinoma.

Cancer statistics should be interpreted with caution. These estimates are based on data from thousands of cases of this type of cancer in the United States each year, but the actual risk for a particular individual may differ. It is not possible to tell a person how long he or she will live with non-melanoma skin cancer.

Statistics adapted from the American Cancer Society's publication, Cancer Facts & Figures 2009.

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