The skin covers the entire surface of the body and it is the largest human organ. The surface of the skin is 1.5 – 2 m ², depending on the height and body mass of the person, and represents approximately 16% of the total body weight. The thickness of the skin depends on the part of the body and it is the thickest on the palms of the hands and soles of the feet, while it is the thinnest on the eyelids. The skin has many functions, and the main one is protection. It forms the boundary between the organism and the environment and protects the body from negative influences such as microorganisms, cold, heat and ultraviolet radiation. Protecting the skin from ultraviolet (UV) radiation is done by the creation and production of the pigment melanin, and vitamin D is also produced in the skin. The skin is built from three layers, the surface epidermis, below which is the dermis and subcutis. In the dermis there are the sweat and sebaceous glands, the roots of the hair, the endings of nerves and lymph and blood vessels. In the epidermis there are several types of cells in multiple layers, and at the bottom of the epidermis in the basal layer are the melanocytes. Melanocytes are dendritic cells that contain granules and produce melanin which gives the skin colour. Skin colour depends on the amount of melanin; lighter skin has less, and darker has more melanin. Clusters of melanocytes form a mole (nevus).
Melanoma is the malignant neoplasm that occurs when there are malignant changes in the melanocytes and they start to uncontrollably divide and grow.