e in size and can spread after reaching a critical depth in the skin. Basal-cell and squamous-cell carcinomas are similar in some ways and different in others. The cure rate for these cancers is about 95 percent when properly treated. Basal tumors do not spread but must be completely and promptly removed. It is very rare for either to spread to organs other than the skin, and they may be diagnosed and treated in the same manner.
Another common skin disorder is actinic keratosis, a precancerous disease caused solely by sun exposure. It usually affects people who had a great deal of sun exposure. The disease consists of smooth, flat, or slightly raised pink spots that later become irregular, scaly, and wartlike and are red or brownish in color.
Although representing only a small percent of reported skin cancers, melanomas are the most virulent and notorious of them all. They affected more than 27,000 Americans in 1989, and about 6,000 of them died. Melanomas begin in the melanocyte--the skin cells that produce the dark protective pigment called melanin. Melanomas consist of melanocyte which has been transformed into cancer cells growing uncontrollably. Once colonies of melanoma cells reach vital internal organs, they are much more difficult to treat. Twenty-five percent of all melanomas come from moles. These brown spots which some people are born with are a great risk, primarily because of their numerous pigment cells. Affected moles or new melanomas often appear with different shades of tan, brown, black or grey, which accounts for their ability to continue to produce melanin. Irregularity of mole shape is also a common sign of melanoma.
Several factors influence the development of melanomas. Not only does the amount of sunlight increase melanoma risk, but experts believe that intense, intermittent periods of sunlight enhance that risk. Fair-skinned, light-haired individuals or those with a family history o...