Understanding Skin Cancer -- the Basics
Types of Skin Cancer continued...
The two most common skin cancers, basal cell carcinoma and squamous cell carcinoma, are nonmelanomas and are rarely life-threatening. They progress slowly, seldom spread beyond the skin, are detected easily, and usually are curable. Basal cell carcinoma, which accounts for nearly three out of four skin cancers, is the slowest growing. Squamous cell carcinoma is somewhat more aggressive and more inclined to spread. In addition, there are a few rare nonmelanomas, such as Kaposi's sarcoma, a potentially life-threatening disease characterized by purple growths and associated with a suppressed immune system and almost always seen in patients with AIDS or the elderly.
Some noncancerous skin growths have the potential to become cancerous. The most common are actinic keratoses – crusty, reddish lesions that may scratch off but grow back on sun-exposed skin.
Who Is at Highest Risk for Skin Cancer?
Skin cancer tends to strike people of light skin color. Dark-skinned people are rarely affected and then only on light areas of the body such as the soles of the feet or under fingernails or toenails. An estimated 40% to 50% of fair-skinned people who live to be age 65 will develop at least one skin cancer. The incidence of skin cancer is predictably higher in places with intense sunshine, such as Arizona and Hawaii. It is most common in Australia, which was settled largely by fair-skinned people of Irish and English descent.
What Causes Skin Cancer?
Excessive exposure to sunlight is the main cause of skin cancer. Sunlight contains ultraviolet (UV) rays that can alter the genetic material in skin cells, causing mutations. Sunlamps, tanning booths, and X-rays also generate UV rays that can damage skin and cause malignant cell mutations. Basal cell carcinoma and squamous cell carcinoma have been linked to chronic sun exposure, typically in fair-skinned people who spend considerable time outside. Melanoma is associated with infrequent but excessive sun exposure that causes scorching sunburns. One blistering sunburn during childhood appears to double a person's risk for developing melanoma later in life.
Fair-skinned people are most susceptible, because they are born with the least amount of protective melanin in their skin. Redheads, blue-eyed blonds, and people with pigment disorders such as albinism are at the greatest risk. But people with many freckles or moles, particularly abnormal-looking ones, may also be vulnerable to melanoma. Workers regularly exposed to coal tar, radium, inorganic arsenic compounds in insecticides, and certain other carcinogens are at slightly higher than normal risk for nonmelanoma skin cancer.