Each year, more than 3.5 million people are diagnosed with some form of it. Most skin cancers form on parts of the body exposed to the sun or in people with weakened immune systems. Fortunately, if caught early, skin cancer is one of the most treatable cancers.
Cancer begins when the very small units of the skin (the cells) begin growing abnormally. When cancer cells begin growing out of control, they can form abnormal tissue called tumors, which replace healthy tissue. If not treated early enough, the cancer cells can spread to other parts of the body.
The skin contains different types of cells. The top layer of skin called the epidermis is mainly made up of flat cells known as squamous cells. Below these cells in the epidermis are round cells called basal cells.
Scattered among the basal cells, in the deepest part of the epidermis, are melanocytes, which are the cells responsible for making a brown pigment called melanin. This pigment gives skin its tan or brown color and protects the deeper layers of the skin from the harmful rays of the sun.
The most common skin cancers form in 1 of 3 epidermal cells (basal, melanocyte or squamous) and are named after the cell in which they form: