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.

Expert review and references

  • American Cancer Society . Melanoma Skin Cancer . 2015 : https://www.cancer.org/.
  • American Society of Clinical Oncology . Melanoma . 2015 : https://www.cancer.net/.
  • National Cancer Institute . Melanoma Treatment (PDQ®) . 2015 : https://www.cancer.gov/.
  • National Cancer Institute . Common Moles, Dysplastic Nevi and Risk of Melanoma . 2011 : https://www.cancer.gov/.
  • Ribas A, Slingluff Cl Jr, Rosenberg SA . Cutaneous melanoma. DeVita VT Jr, Lawrence TS, Rosenberg SA. Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2015: 94:1346-1394.

The skin

The skin is the body’s largest organ. Learn about functions of the skin and the skin’s different layers.

Types of melanoma skin cancer

There are 4 main types of melanoma skin cancer – superficial spreading, nodular, lentigo maligna and acral lentiginous.

Precancerous conditions of the skin

Precancerous conditions of the skin have the potential to develop into melanoma.

Non-cancerous tumours of the skin

Learn about non-cancerous skin growths, such as moles and skin tags, which do not spread to other parts of the body and are not usually life-threatening.

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