Melanoma
(Skin Cancer · Cancer of the Skin · Skin Tumour)
In this condition factsheet:
The Facts on Melanoma
Melanoma is the most serious form of skin cancer. In Canada, an estimated 9,000 people are diagnosed with melanoma each year, and approximately 1,200 of them die of it.
It's important to know that melanoma only has its most serious consequences if it goes undiagnosed. It's fairly easy to recognize and is highly treatable if caught early.
Some risk factors for developing melanoma include:
- excessive exposure to the sun and ultraviolet (UV) radiation
- history of blistering burns (especially during childhood)
- presence of atypical moles
- having a large number of moles (i.e., more than 50 moles)
- light skin complexion (often blond or red hair with green, blue, or grey eyes)
- skin that tends to freckle or burn easily rather than tan
- personal or family history of skin cancer
- a weakened immune system
- taking medications that increase the skin's sensitivity to UV light
- having had childhood cancer with radiation treatment and immunosuppression (less common)
Causes of Melanoma
Cancer is caused by mutations of the genetic material (DNA) in a cell. The mutated genes tell the cell to divide and keep dividing, eventually producing an uncontrolled growth of cells with the same mutation. We don't understand the process fully, but we know of many carcinogens, substances that provoke cancer or increase your chance of getting it.
For skin cancer, the primary carcinogen is sunlight. Studies have shown that melanoma is more common among people who have spent a lot of time in the sun. The damage caused by UV light can lead to mutations. The incidence of melanoma is rising, a reflection of the boom in sunbathing since the Second World War.
People of African descent are less likely to get melanoma than Caucasians, though they can get a rare form that appears on mucous membranes (e.g., on the inside of the mouth). Among Caucasians, paler people are more susceptible. The risk goes up for those with blue or green eyes, fair hair, and freckles.
Most people get the bulk of their sun exposure as children, and people who had severe sunburn before age 18 are at higher risk for skin cancer. Along with UV light from the sun or indoor tanning beds, X-rays have been associated with an increased risk for melanoma, as has exposure to radium or arsenic.
Skin cells called melanocytes provide the brown pigment that results when we tan in the sun. Melanoma always starts in melanocytes. It can take root in existing moles on the skin, which are actually groups of melanocytes, or it can start in a single melanocyte cell in normal skin.
Some moles are more risky than others. Dysplastic nevi are moles that look abnormal in some way and may turn into melanoma in the future. The way to recognize dysplastic nevi is as simple as ABCDE – they will have one or more of the following characteristics:
- Asymmetry: The mole is not round like normal moles, but is odd-shaped or elongated.
- Border: The border is irregular, like a rugged coastline on a map, and it fades into the skin rather than making a sharp edge.
- Colour: The mole has areas of different colour, possibly including white, blue, red, or (especially) black.
- Diameter: It is larger than the size of a pencil eraser (or greater than 6 mm).
- Evolution: It changes in colour, shape, size, or symptoms (e.g., bleeding, itching, crusting).
Symptoms and Complications of Melanoma
Melanoma is a visible kind of cancer, unlike others that start inside the body (such as breast cancer or prostate cancer). Melanoma often causes changes that are visible and apparent. What's important is to recognize the signs and have a doctor check any suspicious moles.
A changing mole doesn't necessarily mean cancer, but it certainly needs looking at. A new mole on previously clear skin is equally significant. See a dermatologist or your family doctor about any of the following changes:
- A mole's border becomes ragged or indistinct, or pigment (colouring) seeps into neighbouring skin.
- A mole grows, changes colour, becomes raised from the skin, or develops small irregular bumps or crags.
- A mole becomes hard, crusty, or irritated, or is bleeding.
- An ulcer or cut doesn't heal after a month.
- There are black spots under the base of the nails.
- There is any new growth or patch of abnormal colour on the skin.
Melanoma is a very dangerous skin cancer if left untreated because it can spread to other parts of the body and can even lead to death.
