Sun and Skin Cancer When Ellen was a teenager, she loved to be out in the summer sun. She ran, she worked in her garden. She would swim and sit by the pool for hours soaking up the sunshine. And she never got tired of hearing people tell her how great her tan looked. As Ellen got older, she continued to spend lots of time outdoors in the sun. By the time she was in her forties, Ellen's skin had developed a weathered look, with small creases(褶皱) and wrinkles. That was okay, but she also began to notice brown patches developing on her face and hands. Ellen saw a doctor and found out she had a relatively mild case of skin cancer. Ellen was lucky. Her cancer was detected early. With early treatment, she was completely cured. But Ellen began—late in life to pay for all those years she had spent in the sun. Ellen isn't unusual. The athletic, bronzed bodies we see in magazine ads and TV commercials constantly tell the idea that a good tan means health, attractiveness, and fun. The result is that many people believe those ads. And they spend a lot of time in the sun—often just trying to get tan. That golden or bronze color may look nice, hot skin doctors know that sitting in the sun until you are baked several shades darker is not such a hot idea. According to the National Cancer Institute, over 400,000 Americans can expect to get some form. of skin cancer this year. Most of these people will be 40 or older. However, skin cancer—especially skin cancer caused by exposure to the sun—can often take many years to develop. So it's never too early to protect yourself in the sun. What's a tan? As soon as warm weather arrives, lots of people who don't already have dark skin want to start working on their tans. But a tan isn't really nature's way of making you look gorgeous. A tan is your skin's defense against the sun's ultraviolet(UV) radiation. UV rays damage skin cells. So when you decide to have a marathon roasting session in the sun, cells in your skin called melanocytes(黑色细胞) go to work overtime. They produce an extra supply of melanin(黑色素), the brown/black pigment(色素) that gives your skin its color. That extra melanin makes your skin darker, and that's why you 'tan'. Think of your tan as a shield of melanin your body produces to block out the UV radiation. The problem is, it is a weak shield at best. There's no way for your body to protect itself fully against the sun's harmful rays—especially if you expose yourself to the sun hour after hour, clay after day, year after year. As you get older, the buildup of many hours in the sun means more of a chance for skin damage and possibly skin cancer. This skin damage takes two general forms. Some UV attacks supporting cells in the lower layer of the skin, called the dermis(真皮). That causes skin to get dry, tough, and wrinkled. Even more serious is the damage the sun's UV rays can do to the DNA of skin cells. DNA is the genetic blueprint that cells use to reproduce. With Damaged DNA, the skin may produce mutated(使变异，突变)cells that start to grow in an uncontrolled way: skin cancer. Nature gives you a clue about how much sun is enough by the color of your skin. If your skin is light, you don't have much built-in protection against the sun. You probably tan very little, if at all. So be very careful in the sun. If you have dark skin and dark hair, you can probably stand a bit more sun exposure. Just don't be fooled into thinking you can stay out in the sun indefinitely. You can't. People with dark skin also get sunburned and can suffer skin damage. It just takes a bit longer for the damage to show up. Types of skin cancer The three most common types of skin cancer are all connected with exposure to the sun. The most common of these is basal cell carcinoma. Basal cancers often look like waxy, pearly growths or red, scaly patches. They appear most often on the