Skin cancer can be divided into three main categories a fact that most people forget when discussing the causes and risk factors for different types of this disease. The categories are:

Basal cell carcinoma is the most common form of skin cancer, with an estimated 400,000 cases reported annually.
It is almost always a benign cyst or a topical lesion that is completely curable and almost never spreads to other parts of the body. Potential risk factors include heredity, sunburn incidence, cigarette smoking and a high-fat diet.

Squamous cell carcinoma is the second-most common form of skin cancer, with an estimated 100,000 cases reported annually. Benign in 98 percent of cases, squamous cell carcinoma seldom spreads and, like basal cell carcinoma, is almost always completely curab when detected. Heredity, sunburn incidence, cigarette smoking and a high-fat diet have all been implicated as potential risk factors for this form of skin cancer. Interestingly, this disease often appears in scarred or burned skin, and tumors in those sites account for 75 percent of all spreading in sites that had nothing to do with sun exposure. In sites where sunburn and overexposure are suspected risk factors, this tumor is malignant in only one-half of one percent of cases.

Melanoma is the most misunderstood of the three types of skin cancer, with an estimated 32,000 cases reported annually. Heredity, intermittent sunburns and severe burns as a child seem to be the most probable risk factors. What people don't seem to understand is that melanoma appears most often on parts of the body that do not receive regular sun exposure, and is more common in people who work indoors than in those who work outdoors. The conventional thinking is that people who are out in the sun frequently are less-susceptible to sunburns when they are outdoors, which may explain why outdoor workers aren't as likely to get melanoma. Still, some studies have suggested that genetic predisposition to sunburn is the most important link, and that sunburn incidence itself may not even be the risk factor.

Because sunburn incidence, or merely an individual's genetic susceptibility to sunburn are suspected risk factors for most skin cancer cases, the professional indoor tanning industry is playing an important role in reducing the incidence of sunburn by teaching tanners how to maximize the benefits of regular, moderate sun exposure while minimizing the risks of either too much or too little sunlight. Our efforts appear to be working. Sunburn incidence has declined among indoor tanners in the past five years, but has increased in the general population. Clearly, it is the non-tanners who are doing most of the burning. Those who get intermittent sun exposure on holidays and weekends are most likely to sunburn when they inevitably do go outside.