The skin protects against heat, sunlight, injury, and infection. Skin also helps control body temperature and stores water and fat. Skin cancer is the most common type of cancer. It usually forms in skin that has been exposed to sunlight, but can occur anywhere on the body.
Skin has several layers. Skin cancer begins in the epidermis (outer layer), which is made up of squamous cells, basal cells, and melanocytes.
Skin cancer starts in the cells of the skin. Some other types of cancer start in other parts of the body and can spread to the skin, but these are not skin cancers.
There are several different types of skin cancer. There are 3 main types of skin cancers:
- Basal cell skin cancers (basal cell carcinomas)
- Squamous cell skin cancers (squamous cell carcinomas)
Squamous cell and basal cell skin cancers are sometimes called nonmelanoma skin cancers. Nonmelanoma skin cancer usually responds to treatment and rarely spreads to other parts of the body. Melanoma is more aggressive than most other types of skin cancer. If it isn’t diagnosed early, it is likely to invade nearby tissues and spread to other parts of the body. The number of cases of melanoma is increasing each year. Only 2 percent of all skin cancers are melanoma, but it causes most deaths from skin cancer.
Rare types of skin cancer include Merkel cell carcinoma, skin lymphoma, and Kaposi sarcoma.
How common is skin cancer?
The incidence of both non-melanoma and melanoma skin cancers has been increasing over the past decades. Currently, between 2 and 3 million non-melanoma skin cancers and 132,000 melanoma skin cancers occur globally each year. One in every three cancers diagnosed is a skin cancer and, according to Skin Cancer Foundation Statistics, one in every five Americans will develop skin cancer in their lifetime.
As ozone levels are depleted, the atmosphere loses more and more of its protective filter function and more solar UV radiation reaches the Earth’s surface. It is estimated that a 10 per cent decrease in ozone levels will result in an additional 300,000 non-melanoma and 4,500 melanoma skin cancer cases. The global incidence of melanoma continues to increase – however, the main factors that predispose to the development of melanoma seem to be connected with recreational exposure to the sun and a history of sunburn. These factors lie within each individual’s own responsibility.