Skin Cancer

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 exposed to sunlight but can occur anywhere.
The 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 body parts and can spread to the skin, but these are not skin cancers.
There are several different types of skin cancer. There are three main types of skin cancers:
Basal cell skin cancers (basal cell carcinomas)
Squamous cell skin cancers (squamous cell carcinomas)
Melanomas
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 body parts. Melanoma is more aggressive than most other types of skin cancer. If it isn’t diagnosed early, it will likely invade nearby tissues and spread to other body parts. 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.