What is non-melanoma skin cancer?

Non-melanoma skin cancer starts in the cells of the skin. A cancerous (malignant) growth is a group of cancer cells that can grow into and destroy nearby tissue. It can also spread (metastasize) to other parts of the body, but this is rare with non-melanoma skin cancer.

The skin is the body’s largest organ. It covers your entire body and protects you against harmful factors from the environment such as the sun, hot temperatures and germs. The skin controls body temperature, removes waste products from the body through sweat and provides the sense of touch. It also helps make vitamin D.

Cells in the skin sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous (benign) growths such as dermatofibromas, moles, skin tags and warts.

Changes to cells of the skin can also cause precancerous conditions. This means that the abnormal cells are not yet cancer, but there is a chance that they may become cancer if they aren’t treated. A precancerous condition of the skin is actinic keratosis.

But in some cases, changes to skin cells can cause non-melanoma skin cancer. Most often, non-melanoma skin cancer starts in round cells called basal cells found in the top layer of the skin (epidermis). This type of cancer is called basal cell carcinoma (BCC) and makes up about 75%–80% of all skin cancers. Non-melanoma skin cancer can also start in squamous cells of the skin, which are flat cells found in the outer part of the epidermis. This type of cancer is called squamous cell carcinoma (SCC) and makes up about 20% of all skin cancers. BCC and SCC tend to grow slowly and are often found early.

Rare types of non-melanoma skin cancer can also develop. These include Merkel cell carcinoma and cutaneous T-cell lymphoma.