The primary types of skin cancer are:
Basal cell carcinomas: This is the most common form of skin cancer, accounting for nearly 80 percent of all cases, according to the American Cancer Society. These cancers occur in the cells just below the skin's surface.
Squamous cell carcinomas: This form of skin cancer accounts for about 20 percent of all cases. Squamous cells are also found in the throat, the lining of the digestive system and respiratory tract and major organs like the liver and kidneys.
Merkel cell carcinomas: Though very rare, this cancer is an aggressive form of skin cancer. Merkel cells, sometimes called touch cells because they give the skin its ability to sense touch, are found below the epidermis, nestled next to nerve endings.
Kaposi's sarcoma (KS): This type of skin cancer may appear as purplish blotches or lesions on the skin (usually on the face or legs), but it may also form inside the mouth or in lymph nodes. In rare cases, lesions may develop in the lungs, causing breathing problems.
Lymphoma of the skin: Lymphoma, which is cancer of the lymphatic system, may form in a variety of locations in the body, including the spleen, lymph nodes, thymus and skin. This cancer may appear as red or purple patches, moles or pimples on the skin that may itch or ulcerate. Other symptoms may include fatigue and weight loss.