What is melanoma?

Melanoma is a cancer that most often starts in the skin. The skin is the body’s largest organ. It protects the organs inside your body from injury, infection, heat and ultraviolet light from the sun. The skin helps control your body temperature and gets rid of waste materials through the sweat glands. It also makes vitamin D and stores water and fat.

The skin has two main layers. The layer at the surface is called the epidermis. Below the epidermis is the inner layer, the dermis.

Deep in the epidermis are cells called melanocytes. Melanocytes make melanin, which gives colour to your skin. When skin is exposed to the sun, the melanocytes make more melanin and cause the skin to tan or darken. Sometimes melanocytes cluster together and form moles (called nevi). Moles are common and are usually not cancerous. The dermis contains nerves, blood vessels, sweat glands, oil glands and hair follicles.

There are three types of skin cancer.

• Squamous cell skin cancer starts in the squamous cells (thin flat cells found on the surface of the skin).
• Basal cell skin cancer starts in the basal cells (round cells that lie under the squamous cells).
• Melanoma starts in the melanocytes.

Melanoma is less common than squamous cell and basal cell skin cancers (sometimes called non-melanoma skin cancers). Melanoma can start in other places in the body where melanocytes are found, such as the eyes, the mouth, the vagina or under the fingernails. These types of melanoma are rare.

Last modified on:  07 January 2009

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