Skin cancers are broadly divided into two types- Melanoma and non-melanoma. Melanoma is the most deadly of skin cancers. The three major skin cancers that are diagnosed in almost all the cases are- Basal Cell Carcinoma, Squamous Cell Carcinoma and Melanoma. All these cancers are named after the type of cell in which they begin. Thus Basal Cell Carcinoma begins in the skin cells located in the lowest layer of epidermis, which is called the basal layer. Squamous Cell Carcinoma develops from the upper layer of the epidermis named squamous layer and Melanoma begins from the melanocytes. Melanocytes are the cells that give skin its color.
Basal Cell Cancer
It is one the most frequently diagnosed skin cancers. It affects the basal cells, which are located in the bottom layer of the epidermis. Malignant cells proliferate excessively from the epidermis resulting in a tumor. The incidence of basal cell cancer increases with age. Almost all people diagnosed with basal cell carcinoma can expect to live at least another 5 years.
Though it generally does not spread to distant sites (metastasize), and is, therefore, less fatal. Basal cell carcinoma can invade normal tissue and damage deeper tissues of muscles and bones, and disfigure the skin. On its return, Basal cell carcinoma can be more aggressive. During recurrence it may grow faster and cause more tissue damage.
Squamous Cell Cancer
This type of cancer involves the malignancy and proliferation of squamous (flat, scaly) cells. The squamous cell or keratinocyte, is the most abundant cell in the epidermis. Cutaneous squamous cell carcinoma is usually localized, but it can spread (metastasize). It is easily treated and cured when confined to the skin. Most cutaneous SCC develops in individuals with known factors, such as excessive exposure to the sun.
Malignant melanoma is an accelerated, metastatic type of skin cancer that originates in the cells of the epidermis. In this disorder, pigment-producing cells called melanocytes become cancerous, grow, and multiply at a devastating rate. Although melanoma is the least common type of skin cancer, it is the most serious form of skin cancer. Melanoma may be cured, if caught and treated early, but it is rarely curable in its later stages.
Melanoma skin cancer cells are more likely than non-melanoma skin cancer cells to spread or metastasize. This means that they break away from the original tumor, travel through the blood or lymphatic vessels, and then grow within other parts of the body.
The most well documented risk factor for malignant melanoma is exposure to UV radiation.
Melanoma affects equal number of men and women and affects any part of the body. It usually appears after age 50, though it can develop at any age. People with light skin are far more likely to develop melanoma than dark-skinned people.