As is well known, skin is the largest organ in human body, making up 12–15% of body weight, with a surface area of 1–2 square meters. There are two main layers of skin: the top layer is called the epidermis, and the inner layer is called the dermis. Malignancies are always found in the epidermis, and it contains three kinds of cells: squamous, basal cells, and melanocytes. Squamous is on the surface and looks flat and scaly; basal cells are round cells; and melanocytes give color to skin. The dermis contains blood vessels and sweat glands. It is used to keep skin from drying out.
People whose skin is exposed to sunlight for longer amounts of time are more prone to develop skin cancer. Australia and New Zealand are the two countries with the highest rates of skin cancer incidence in the world, with rates that are almost four times that of the United States. Based on the statistics in 2008, 59,695 people in the US were diagnosed with melanomas of the skin, and 8,623 people died from it.
Skin cancers are named after three kinds of cells in the epidermis from which they arise. Basal cell cancer arises on basal cells and is the most-common skin cancer. Squamous cell cancer is found on squamous cells and is less common. Basal and squamous cell cancers are called nonmelanoma skin cancer and are less dangerous than melanoma, which develops on melanocyte cells. Melanoma is less common than nonmelanoma skin cancer, but it is more likely to spread and become fatal.
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