Melanoma is not the most common type of skin cancer, but it is the most serious. There are many risk factors for melanoma, including one major risk factor that is largely avoidable - overexposure to the sun.
Melanoma is a form of skin cancer that arises when the pigment-producing cells (melanocytes) mutate and become cancerous. Most pigment cells are found in the skin, although melanoma can also occur in the eyes (ocular melanoma) and other parts of the body, such as the intestines (this is rare). It is very rare in people with dark skin.1,2
Melanoma is just one type of skin cancer, and is much less common than basal cell and squamous cell skin cancers. However, melanoma is an especially dangerous type of skin cancer because it is more likely to spread. 1,2
This article focuses on melanoma because it accounts for the majority of deaths from skin cancer each year. Much of the information regarding the prevention and treatment of melanoma also applies to the more common, but less deadly, skin cancers and pre-cancerous lesions.2
Squamous cell carcinoma and basal cell carcinoma are two such types of non-melanoma skin cancer. Basal cell is the most common form and usually grows very slowly, rarely spreading beyond the skin. Squamous cell carcinoma also rarely metastasises. Both types are known as keratinocyte skin cancers due to their involvement of keratin-producing skin cells and their appearance under the microscope. Like melanoma, squamous cell and basal cell carcinomas are linked to sun exposure.2
Contents of this article:
Here are some key points about melanoma. More detail and supporting information is in the body of this article.
- Melanoma is the rarest, but the most dangerous, form of three common types of skin cancer.
- Melanoma accounts for just 2% of skin cancer cases but almost 10,000 of the >13,000 skin cancer deaths each year (American Cancer Society).
- Numerous risk factors have been identified for melanoma, and the incidence appears to be increasing for people under the age of 40, especially in women.
- Repeated overexposure to the sun is the major avoidable risk factor for melanoma - not getting sunburnt is the best prevention against skin cancer.
- Diagnosis of skin cancer is made initially by the appearance of the skin, and confirmed by biopsy sample.
- Self-monitoring of moles and other markings on the skin helps with early detection of skin cancer.
- Treatment usually aims to completely remove skin cancer tumors, and is curative if done at the cancer's earliest stage.
Melanomas can develop on any part of the skin. Certain areas are more prone than others, however. In men, the trunk (chest and back) is most likely to be affected by melanoma. In women, the legs are the most common site of melanoma. Other common sites are the neck and face.2
Skin cancer is the most common type of cancer in the US, according to the National Cancer Institute.1
According to the American Cancer Society, about 73,870 new melanomas will be diagnosed in 2015 (about 42,670 in men and 31,200 in women), and about 9,940 people are expected to die of melanoma (about 6,640 men and 3,300 women). Almost a further 50,000 cases are diagnosed with an early form of the disease.1
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Causes of melanoma
As with all cancers, research is ongoing into the causes of melanoma. People with certain types of skin are more prone to developing melanoma, with the following factors associated with an increased incidence of skin cancer:2,3
Change of appearance in skin moles should raise suspicion of melanoma.
- High freckle density or tendency to develop freckles after sun
- High number of moles
- Five or more atypical moles
- Presence of actinic lentigines (small gray-brown spots also known as liver spots, sun spots, or age spots)
- Giant congenital melanocytic nevus (brown skin marks present at birth - birth marks)
- Pale skin that does not tan easily and burns; light-coloured eyes
- Red or light-coloured hair
- High sun exposure, particularly if it produces blistering sunburn, and especially if sun exposure is intermittent rather than regular
- Age - risk increases with age
- Family or personal history of melanoma
- Being female
- Having an organ transplant.
Only one of the above risk factors stands out as avoidable - high sun exposure and sunburn. A report by the World Health Organization estimated that the number of early deaths worldwide caused by excessive exposure to the sun's UV (ultraviolet) radiation was 60,000 in the year 2000; many of these people died from melanoma.4
Avoiding overexposure to the sun, and taking steps to prevent sunburn, are hugely important in lowering the risk of skin cancer. This includes avoiding the use of tanning beds as these are also a source of damaging UV rays.2
Symptoms of melanoma
As with other forms of cancer, the early stages of melanoma may not produce any symptoms. This is why active surveillance is heavily promoted by cancer charities and public health organisations, so as to spot early signs of the disease. Changes in the appearance of the skin are key indicators of melanoma and are also used in the diagnostic process).
The Melanoma Research Foundation has produced a web page that compares pictures of melanoma with those of normal moles. This American non-profit organization also lists the following symptoms and signs that should prompt suspicion of skin cancer and necessitate a visit to the doctor:5
- Skin change - a new spot or mole, or a change in color, shape or size of a current spot or mole
- Skin sore that fails to heal
- Spot or sore that becomes painful, itchy, tender or bleeds
- Spot or lump that looks shiny, waxy, smooth or pale
- A firm red lump that bleeds or appears ulcerated or crusty
- A flat, red spot that is rough, dry or scaly.
The ABCDE examination of skin moles is also a key way to reveal suspect lesions.
Melanoma tests and diagnosis
Most cases of melanoma affect the skin, usually producing changes in existing moles.5 For this reason, it is possible for a person to detect the early signs of melanoma themselves by regularly examining moles and other pigmented blemishes and freckles.
Any changes in the appearance of the skin should prompt further examination by a health professional. The back should also be checked regularly, especially as 1 in 3 melanomas in men occur on the back; a partner, family member, friend or physician can help check the back and other hard-to-see areas.2
Cancer doctors are most concerned with lesions that 'stand out from the crowd'3 - and they describe five simple characteristics to look out for in the ABCDE of melanoma appearance:1,6
- Asymmetric: whereas normal moles are typically round and symmetrical, whereas one side of a cancerous mole is likely to look different from the other side - not round or symmetrical
- Border: this is likely to be irregular rather than smooth - ragged, notched or blurred
- Color: melanomas tend not to be of one color but to contain uneven shades and colors, including varying black, brown and tan, and even white or blue pigmentation
- Diameter: a change in the size of the mole, or a mole that is larger than a normal mole (more than a quarter inch in diameter) can indicate skin cancer
- Evolving: a change in a mole's appearance over a period of weeks or months can be a sign of skin cancer.
The American Academy of Dermatology (AAD) has produced a poster featuring this ABCDE method to help improve awareness of how to spot skin cancer.7
The AAD also offers a body mole map for self-monitoring skin.
Doctors may score appearance in a similar way, to rate their suspicion of skin cancer and determine the need for urgent referral to a cancer specialist.3
The higher the score, the greater the suspicion, although just one point is enough to take action if there is any concern about cancer. Scoring three points or more on the following results in a strong suspicion of skin cancer:3
- Two points for each of the following 'major' features of a lesion: change in size, irregular shape or border, irregular color
- One point for each of the following 'minor' features: largest diameter is 7mm or more, inflammation, oozing or crusting of the lesion, change in sensation (including itch).
In 2011, the U.S. Food and Drug Administration (FDA) approved a skin cancer detection device called MelaFind, manufactured by MELA Sciences. This device was designed to aid in the detection of melanoma, and was approved for use by qualified, trained dermatologists and other clinicians.
The device was found to have a 98.4% sensitivity when detecting melanoma, compared to a 78% success rate by dermatologists.10 Despite the success of the device in clinical trials, MELA Sciences have recently voluntarily recalled MelaFind due to a lack of approval for the user interface. It is not yet known whether the device will become available again after approval is obtained for the interface.
Doctors may use microscopic or photographic tools to help them visualize a lesion.2 If a doctor suspects skin cancer, the patient will be referred urgently to a cancer specialist and a biopsy will be arranged to test the lesion. A biopsy is a procedure where a sample of the lesion is taken for examination in the laboratory. A biopsy may be taken by the primary care doctor themselves but is usually performed by the specialist to whom a patient is referred.1,3,6 There are four types of biopsy:1,6
- Shave: where some of the tissue is scraped away with a thin, sharp blade
- Punch: where a circular plug of tissue is removed
- Incisional: where tissue is removed by scalpel
- Excisional: where the whole lesion is removed - typical if the lesion is a suspected melanoma.
The choice of biopsy will depend on the size and location of the lesion, among other factors, with an excisional biopsy typically performed if the lesion is a suspected melanoma.2
As with other types of cancer, testing of skin cancer also indicates the stage of the cancer.2
Staging describes how advanced (widespread) the disease is and provides doctors with information to guide treatment decisions. The American Joint Commission on Cancer recommends the TNM staging system for skin cancers:2
- T score from 0 to 4 based on the thickness of the tumor
- N score from 0 to 3 based on how nearby lymph nodes are affected
- M score based on metastasis (spread) to other parts of the body; M0 is no metastases, M1a, M1b and M1c indicate varying degrees of metastasis.
The above is a brief summary of staging a cancer diagnosis, but oncologists work with much more complex detail.2 Staging becomes more relevant if there has been spread from the primary melanoma.
Treatment and prevention of melanoma
The treatment of skin cancer is similar to that of other cancers, except that the location of the cancerous growth in the skin generally means that it is possible to completely remove the cancer (something which is much more difficult for internal cancers). As the aim of skin cancer therapy is to completely remove the cancer, surgery is the most common treatment for melanoma.1
A melanoma is often surgically removed at the same time as a biopsy is taken for testing. Otherwise, the specific surgical operation involves removal of the lesion and some of the normal tissue around it - a border or margin around the tumor or suspected tumor.2
In cases where a melanoma covers a large area of skin, surgery to remove the melanoma may also involve the use of skin grafts. Where the cancer is suspected to have penetrated into the lymph nodes, a lymph node biopsy may be performed; a sentinel lymph node biopsy is a relatively new procedure that may spare lymph nodes during diagnosis.9
Other, less common treatments for skin cancer include chemotherapy, photodynamic therapy (light and drug therapy - not usually used in melanoma cases), biological therapy (drugs that work with the immune system), and radiation therapy (rarely used for skin cancer).2
Despite warnings against overexposure to the sun, it remains important to get a little sun exposure as this enables our bodies to produce vitamin D, an important nutrient for the prevention of diseases such as rickets and osteomalacia.3 As such, sensible sun exposure is advised.
Repeated episodes of severe sunburn increase the risk of melanoma.
The time it takes to produce sufficient vitamin D is less than the time it takes to get sunburnt, meaning that enjoying the sun safely can help us to maintain optimal vitamin D without dramatically increasing the risk of skin cancer. When higher levels of vitamin D are needed, this may necessitate the use of supplemental vitamin D, so as to ensure good nutrition while minimizing the risk of skin cancer. Higher vitamin D intake may be needed by people who:3
- Have naturally brown or black skin
- Cover their whole body and head with clothing
- Stay indoors all the time
- Are pregnant
- Are vitamin D-deficient and breastfeeding.
Avoiding excessive exposure to ultraviolet radiation can reduce the risk of skin cancer. This can be achieved by:3
- Avoiding sunburn
- Wearing clothes that protect against the summer sun
- Using sunscreen with a minimum sun protection factor (SPF) of 15, but preferably SPF 20-30, with 4- or 5-star UVA protection
- Not spending longer in the sun because sunscreen is used
- Liberally applying sunscreen about half an hour before going out, and applying it again after half an hour.
- Reapplication should then be every two hours to maintain adequate protection
- Avoiding the highest sun intensity between 11am and 3pm, by finding shade. Outdoor workers need to take particular care
- Protecting children by trying to keep them in the shade, with clothing, and by applying SPF 50+ sunscreen
- Keeping babies out of direct sunlight.
Doctors recommend that tanning booths, lamps, and sunbeds are not used.3
Several studies have found that caffeine intake is negatively correlated with the incidence of melanoma, with the effect of caffeine appearing to be strongest in women who consume at least 393 mg of caffeine a day.11 This equates to around four cups of coffee.
Starving melanoma cells may slow tumor growth. Research published in The International Journal of Cancer in January 2014 found a way to block cancer cell access to glucose.
Sunscreen alone "not enough" to protect against melanoma. Researchers publishing their findings on mice in Nature in June 2014 conclude: "UV light has long been known to cause melanoma skin cancer, but exactly how this happens has not been clear. These studies allow us to begin to understand how UV light causes melanoma."
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