Skin cancer basics
What is skin cancer?
Skin cancer is cancer affecting the skin, often due to too much sun exposure over the years.
More than 2,200 people in the UK died from malignant melanoma skin cancer in 2011.
Simple precautions can help reduce the risk of skin cancer, including using sun protection of at least SPF15, covering up, staying in the shade, and avoiding sunburn.
Types of skin cancer
Skin cancers fall into two major categories: melanoma and non-melanoma.
Melanoma can start in heavily pigmented tissue such as a mole or birthmark as well as in normally pigmented skin. Melanoma usually appears first on the torso or back, although it can arise on the palm of the hand, on the sole of the foot, under a fingernail or toenail, in the mucous linings of the mouth, vagina or anus, and even in the eye.
Melanoma is an extremely aggressive, life-threatening cancer. It is readily detectable and usually curable if treated early, but it progresses faster than other types of skin cancer and tends to spread beyond the skin to affect the bones or brain. Once this occurs, melanoma becomes very difficult to treat and cure.
The two most common skin cancers, basal cell carcinoma and squamous cell carcinoma, are non-melanomas, which 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. There are also a few rare non-melanomas such as Kaposi's sarcoma, a potentially life-threatening disease characterised by purple growths and associated with a suppressed immune system - it is almost always seen in patients with AIDS.
Some technically non- cancerous 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. Another precancerous skin growth, cutaneous horns, appear as funnel-shaped growths that extend from a red base on the skin.
Who is at highest risk of skin cancer?
Skin cancer tends to affect people of light skin colour. 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 65 will develop at least one skin cancer. The incidence of skin cancer is predictably higher in countries with intense sunshine, and is most common in Australia. Non-melanoma skin cancer is the most common type of cancer in the UK, with around 100,000 new cases every year.
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, sun beds 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 work outside. Melanoma is associated with infrequent but excessive sunbathing that causes sunburn. 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. Redheads, people with blonde hair and blue eyes, 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 of non-melanoma skin cancer.