Skin cancer is a malignant growth of the external surface or epithelial layer of the skin. It is the growth of abnormal cells capable of invading and destroying other associated skin cells. Skin cancer is often subdivided into either melanoma or non-melanoma. Melanoma is a dark-pigmented, usually malignant, tumor arising from a skin cell capable of making the pigment melanin (a melanocyte). Melanoma can spread throughout the body via the bloodstream or lymphatic system.
Cumulative sun exposure is considered a significant risk factor for non-melanoma skin cancer. High incidence has been noted in individuals with freckles, light hair, and light complexion; in individuals with darker skin, the palms, soles, mucous membranes, and other areas of light pigmentation are the most common sites for melanomas.