The three most common types of skin cancer stem from basal cells, squamous cells and melanocytes, all of which are located in the outermost layer of the skin, the epidermis. According to 2009 data released from the American Cancer Society, there are more than two million cases of basal and squamous cell skin cancer yearly in the United States, and almost 69,000 cases of skin cancer that originate from melanocytes.
Basal Cell Carcinoma
Basal cell carcinoma is the most common type of skin cancer, accounting for 8 out of 10 cases in the United States, according to the American Cancer Society. This type of skin cancer is found most often in areas of the skin that are exposed to the sun such as the face, neck, arms, and legs. Basal cell carcinoma is usually a very slow growing cancer, and very rarely spreads to other areas in the body. Though basal cell carcinoma is often successfully treated by surgical removal, it often recurs. The American Cancer Society reports that almost half of the people who develop basal cell carcinoma, experience a recurrence within 5 years.
Squamous Cell Carcinoma
This type of skin cancer originates from the flat and thin squamous cells of the skin. About 2 out of every 10 people who develop skin cancer have squamous cell carcinoma, according to the American Cancer Society. Like basal cell carcinoma, sun exposure is a common cause of squamous cell carcinoma, and thus, this type of skin cancer often appears on parts of the body exposed to the sun. Squamous cell carcinomas often grow more quickly than basal cell carcinomas, and as such are a more aggressive type of cancer. Squamous cell carcinoma sometimes spreads to the fatty tissue underneath the epidermis, and from there can spread to other sites in the body.
Melanoma
Melanomas are a type of skin cancer that begin in the darkly colored melanocytes that make up moles on the skin. Like the other two types of skin cancer, sun exposure increases the risk that melanocytes will transform into uncontrollably growing cells of melanoma, according to the online medical library, Merck Manuals. Moles that contain melanoma cells often look irregular in shape, and contain spots of different colors. Melanoma can also appear as a solid firm black or gray lump on the skin. Although melanoma is much less common than the other two types of skin cancer, it is responsible for almost 75 percent of the deaths from skin cancer, according to the 2009 report from the American Cancer Society.
