What is malignant melanoma?

Melanoma skin cancer starts in the melanocyte cells of the skin. The skin protects our body from heat, injury, infection, water loss and sunlight. Its outermost layer is called the epidermis, which consists of flat, scaly squamous cells. Squamous cells contain a protein (keratin) that makes the skin strong, but flexible. Basal cells and melanocytes (the cells that give the skin its colour) lie deeper in the epidermis. Beneath the epidermis is the dermis that contains nerves, blood vessels, lymphatic vessels, sweat glands, oil glands and hair follicles.

Melanocytes produce a pigment called melanin that gives the skin its colour and protects it from sun damage. When skin is exposed to the sun, it produces more pigment and tans. Melanocytes often cluster together and form moles (nevi). Most moles are benign, but some may go on to become malignant melanomas.



Melanomas are divided into 4 main types, depending on their location, shape and whether they grow outward or downward into the dermis:

superficial, spreading or flat: grows outwards at first to form an irregular pattern on the skin with an uneven colour
nodular: lumpy and often blue-black in colour may grow faster and spread downwards
acral melanomas: occur on the palms of the hand, soles of the feet or nailbeds
lentigo maligna: usually occur on the faces of elderly people
Melanoma can also start in the mucous membranes of the mouth, anus and vagina, in the eye or other places in the body where melanocytes are found.