The skin has 3 layers . From the outside in, they are:
the epidermis
the dermis
the subcutis.
The top layer of the skin, the epidermis, is very thin and serves to protect the deeper layers of skin and the organs. The epidermis itself has three layers:
an upper
a middle
a bottom layer composed of basal cells.
These basal cells divide to form keratinocytes, (also called squamous cells) which make a substance (keratin) that helps protect the body.
Another type of cell (melanocyte) is also present in the epidermis. These cells produce the pigment called melanin. Melanin gives the tan or brown color to skin and helps protect the deeper layers of the skin from the harmful effects of the sun.
A layer called the basement membrane separates the epidermis from the deeper layers of skin.
What Is Skin Cancer?
Skin cancers are divided into nonmelanomas and melanomas.
Nonmelanomas
Nonmelanomas (usually basal cell and squamous cell cancers ) are the most common cancers of the skin. They are called nonmelanoma because they develop from skin cells other than melanocytes. Because they rarely spread elsewhere in the body, they are less worrisome than melanomas. There are several types of non-cancerous (benign) tumors that develop from other types of skin cells. In fact, most tumors of the skin are not cancerous and rarely if ever turn into cancer.
Melanomas
Melanoma is a cancer that begins in the melanocytes. Because most of these cells keep on making melanin, melanoma tumors are often brown or black, but this is not always the case. Melanoma most often appears on the trunk of fair-skinned men and on the lower legs of fair-skinned women, but it can appear other places as well. While having dark skin lowers the risk of melanoma, it does not mean that a person with dark skin will never develop melanoma.
Melanoma is almost always curable in its early stages. But it is also likely to spread to other parts of the body. Melanoma is much less common than basal cell and squamous cell skin cancers, but it is far more serious.
