What is melanoma skin cancer?

Melanoma skin cancer starts in melanocyte cells of the skin. A cancerous (malignant) tumour 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.

Melanocytes make melanin. Melanin gives skin, hair and eyes their colour. The skin is the body’s largest organ and covers your entire body. It protects you against harm from things around you like the sun, hot temperatures and germs. The skin controls body temperature, removes waste products from the body through sweat and gives the sense of touch. It also helps make vitamin D.

Melanocytes can group together and form moles on the skin. They appear as bumps or spots that are usually brown or pink. Most people have a few moles. Moles are non-cancerous (benign) tumours.

But in some cases, changes to melanocytes can cause melanoma skin cancer. A change in the colour, size or shape of a mole is usually the first sign of melanoma skin cancer. There are 4 main types of melanoma skin cancer. Superficial spreading melanoma is the most common type. The other types are nodular melanoma, lentigo maligna melanoma and acral lentiginous melanoma.

Melanoma skin cancer can also start in other parts of the body where melanocytes are found, but these types of melanoma are rare. Mucosal lentiginous melanoma develops on the thin, moist lining of some organs or other parts of the body, such as the nasal passages, mouth and anal canal. Intraocular melanoma starts in the eye.

Another type of skin cancer is non-melanoma, and it’s more common than melanoma. Non-melanoma skin cancers start in basal cells and squamous cells of the skin. Find out more about non-melanoma skin cancer.