SQUAMOUS CELL CARCINOMA
Most skin cancers start in the top layer of skin, called the epidermis. There are 3 main types of cells in this layer:
Squamous cells: These are flat cells in the upper (outer) part of the epidermis, which are constantly shed as new ones form. When these cells grow out of control, they can develop into squamous cell skin cancer (also called squamous cell carcinoma).
Basal cells: These cells are in the lower part of the epidermis, called the basal cell layer. These cells constantly divide to form new cells to replace the squamous cells that wear off the skin’s surface. As these cells move up in the epidermis, they get flatter, eventually becoming squamous cells. Skin cancers that start in the basal cell layer are called basal cell skin cancers or basal cell carcinomas.
Melanocytes: These cells make the brown pigment called melanin, which gives the skin its tan or brown color. Melanin acts as the body’s natural sunscreen, protecting the deeper layers of the skin from some of the harmful effects of the sun. Melanoma skin cancer starts in these cells.
Basal cell carcinoma (also called basal cell skin cancer) is most common type of skin cancer. About 8 out of 10 skin cancers are basal cell carcinomas (also called basal cell cancers). These cancers start in the basal cell layer, which is the lower part of the epidermis. These cancers usually develop on sun-exposed areas, especially the face, head, and neck. They tend to grow slowly. It’s very rare for a basal cell cancer to spread to other parts of the body. But if it's left untreated, basal cell cancer can grow into nearby areas and invade the bone or other tissues beneath the skin. If not removed completely, basal cell carcinomas can come back (recur) in the same place on the skin. People who have had basal cell skin cancers are also more likely to get new ones in other places.
About 2 out of 10 skin cancers are squamous cell carcinomas (also called squamous cell cancers). These cancers start in the flat cells in the upper (outer) part of the epidermis. These cancers commonly appear on sun-exposed areas of the body such as the face, ears, neck, lips, and backs of the hands. They can also develop in scars or chronic skin sores elsewhere. They sometimes start in actinic keratoses (described below). Less often, they form in the skin of the genital area. Squamous cell cancers can usually be removed completely (or treated in other ways), although they are more likely than basal cell cancers to grow into deeper layers of skin and spread to other parts of the body. Breakthrough Therapies