What is skin cancer?
Skin cancer develops when normal skin cells turn into malignant cells that can divide without control. The most important cause of skin cancer is exposure to sunlight.
How common is skin cancer?
Skin cancer is very common. In fact, of all types of cancer, basal cell carcinoma of the skin is by far the most frequent. Over recent decades there has been a strong increase in skin cancer, and this increase seems only to be accelerating. It is estimated that 20 to 25% of people will develop skin cancer at some point in their lives.
What causes skin cancer?
By far the most important cause of skin cancer is too much exposure to sunlight. Using a sunbed (tanning bed) also increases the risk. Damage to skin cells from sunlight accumulates over time, and sunburn in childhood can contribute to skin cancer decades later.
The different types of skin cancer
There are several types of skin cancer; some are common, others very rare. The most common ones are basal cell carcinoma, squamous cell carcinoma of the skin, melanoma and Merkel cell carcinoma.
Basal cell carcinoma
Basal cell carcinoma is by far the most common form of skin cancer. It occurs mainly — but not exclusively — on sun-exposed skin, and is being seen at ever younger ages. It usually grows slowly and (almost) never spreads. The most common type is the nodular basal cell carcinoma, classically a glassy tissue with characteristic small blood vessels (telangiectasia) in it. As the tumours grow larger, a small crater can form, on which a crust keeps appearing, falling off after a time, and then returning. A crater-shaped basal cell carcinoma of this kind is also called an ulcus rodens. Basal cell carcinoma can also be superficial in character, then strongly resembling a patch of eczema or fungal infection, but it does not respond to the usual treatment for those. Superficial basal cell carcinomas are seen relatively more often on the trunk and in younger people.
Squamous cell carcinoma
Squamous cell carcinomas are seen mainly in people who have had long-term sun exposure during their lives. They are often found on the face, the crown of the head in (balding) men, and the backs of the hands, forearms and lower legs. They are usually non-glassy tumours with crust formation. Squamous cell carcinomas can spread; the risk depends on the growth pattern, the size and the location on the skin. Those on the ears, nose and lip have an increased risk of spreading. More aggressive squamous cell carcinomas sometimes form no crusts.
Melanoma
Melanoma is a skin cancer that arises from the melanocytes of the skin — the pigment-forming cells. Most melanomas present as dark, mole-like spots that grow in an irregular way. Occasionally a melanoma is wholly or partly without pigment. Melanomas can spread fairly easily; the risk depends mainly on the thickness of the melanoma.
Merkel cell carcinoma
Merkel cell carcinoma is a rare, usually fast-growing and fast-spreading form of skin cancer. It occurs mostly in older people on sun-exposed skin and usually has a pronounced red colour and a strongly dome-shaped growth.
In general, it is important to have skin lesions that grow, change or cause symptoms — pigmented or not — assessed by your doctor or dermatologist.
Frequently asked question
“I was badly sunburned in the past. Is it still worthwhile to protect myself from the sun now — isn’t the damage already done?”
It is certainly important to protect your skin from the sun now as well. Unfortunately a lot of damage may already have been done in the past, and that damage can cause skin cancer to develop. Even if you protect your skin well from now on, the sun damage already present will not disappear. But if the skin continues to be insufficiently protected, damage to the skin cells continues and the process of skin cancer development will only go faster. Good protection with clothing, a hat and sunscreen therefore remains very important — and seek the shade regularly during the sunniest parts of the day.
When to see a doctor
Have any skin lesion that grows, changes, bleeds, will not heal, or looks different from your other spots — pigmented or not — assessed by a doctor or dermatologist.