What is Skin cancer (melanoma)?

Skin cancer (melanoma)

What is melanoma?

Melanoma is a type of skin cancer that usually starts as a dark spot or mole on your skin. It is the most serious type of skin cancer and can spread to other parts of your body. But if you find a melanoma early, treatment works well and can lead to a cure.

Your doctor may call this type of skin cancer malignant melanoma, but it is often simply called melanoma.

More people may be getting melanomas because we're spending more time in the sun.

Key points for people with melanoma

Melanoma is the most serious type of skin cancer.
More people are being diagnosed with melanomas now than 10 years ago.

Source:
Lamberg L.
"Epidemic" of malignant melanoma: true increase or better detection?
Journal of the American Medical Association. 2002; 287: 2201.

¹
You may be able to prevent melanomas by protecting yourself from the sun. To find out more, see Protecting yourself against melanomas.
You're more likely to get a melanoma if you have fair skin, if someone else in your family has had one, or if you have more than 50 moles.

Source:
Sober AJ, Koh HK, Wittenberg GP, et al.
Melanoma and other skin cancers.
In: Braunwald E, Hauser SL, Fauci AS, et al (editors). Harrison's principles of internal medicine. 15th edition. McGraw-Hill, New York, U.S.A.; 2001.

²
If you have a melanoma, you will need surgery to remove it.
If it's found early, melanoma can be cured.
But if your melanoma has already spread to other parts of your body, treatment probably won't cure you.

Your skin

Your skin has special cells called melanocytes. These are found near the skin's surface. Melanocytes protect your skin from sun damage. When you get a melanoma, it starts in these cells.

Here's how melanocytes protect your skin from the sun.

Source:
Martini FH, Ober WC, Garrison CW, et al.
Fundamentals of anatomy and physiology.
5th edition. Prentice Hall, Upper Saddle River, USA; 2001.

Melanocytes contain a chemical called melanin.
Melanin is a dark pigment that protects your skin from sunlight.
When there is a lot of sun, the melanocytes make more melanin and send it toward the surface of your skin. This is how you get a tan.
Even though everyone has about the same number of melanocytes, people from Africa and Asia have darker skin because their melanocytes make more melanin.

What are moles?

Most moles are perfectly normal. Many people are born with them. Moles usually look like small, round, dark spots. They may be slightly raised up. But if their shape or color changes, it may be a sign that you have skin cancer.

To learn what to look out for, see What are the symptoms of melanoma?

What happens in skin cancer?

A melanoma is a kind of skin cancer. Cancers are diseases that start in your own cells. Sometimes cells grow and divide in an abnormal way, making too many other cells. These abnormal cells stick together. This makes a lump that's called a tumor. If the tumor is cancer, the cancer cells can spread to other parts of your body.

Not all tumors are cancer. Some are called benign tumors, which means that they won't kill you, and they won't spread to other parts of your body.

Source:
Cancer Research UK.
Melanoma skin cancer (overview).
Available at http://www.cancerresearchuk.org (accessed on 18 August 2008).

⁴

Melanomas

When you get a melanoma, the skin cells called melanocytes change to become cancer. Melanocytes make the dark pigment called melanin. So, when they grow out of control, they look like a dark spot or mole on your skin.

Finding melanomas early is important because of how they grow and spread.

At first, most malignant melanomas look like moles that got bigger. When they grow this way, they are still near the surface of your skin.
If you get the melanoma treated at this stage, there's a good chance that you can be cured.
After a while, the cancer begins to grow downward, deeper into your skin.
When the cancer cells grow into the lower layers of your skin, they can get into your blood vessels or your lymph system. The lymph system is a network of vessels that is similar to your blood system, but carries

lymph fluid
Lymph is a clear or whitish liquid that is collected from all over the body and flows through the lymphatic vessels and lymph nodes (also called glands). It contains proteins and fats, some red blood cells, and many white blood cells, especially lymphocytes. Lymphocytes help the body fight infection.

lymph fluid instead of blood. The vessels of the lymph system pass through

lymph nodes
Lymph nodes (also called glands) are small, bean-shaped lumps that you cannot usually see or easily feel. They are located in various parts of the body, such as the neck, armpit and groin. Lymph nodes filter the lymph fluid and remove unusual things, such as bacteria and cancer cells.

lymph nodes, which are small groups of special cells. Lymph nodes filter the fluid that travels through them.
Cancer cells can get trapped in your lymph nodes and start growing there, or they can travel on to other parts of your body. Cancer cells can also travel through your blood vessels.
If the cancer cells get into your blood or lymph system, the melanoma can spread to other parts of your body. When cancer spreads in this way it is called metastasis.

Source:
Slominski A, Wortsman J, Carlson AJ, et al.
Malignant melanoma.
Archives of Pathology and Laboratory Medicine. 2001; 125: 1295-1306.

⁵
When melanoma cells spread into your body from your skin, they most often go to the nearest lymph nodes and then to the lungs.

Source:
National Cancer Institute.
What you need to know about skin cancer.
January 2005. Available at http://www.cancer.gov/cancertopics/wyntk/skin (accessed on 4 December 2007).

⁶ You have lymph nodes throughout your body. For example, in your groin, your neck and under your arms.

Different types of melanoma

Melanomas usually grow in the skin, but sometimes they're found in the eye or other parts of the body, such as the stomach.

Source:
National Cancer Institute.
What you need to know about skin cancer.
January 2005. Available at http://www.cancer.gov/cancertopics/wyntk/skin (accessed on 4 December 2007).

⁶ However, it's rare for melanomas to grow in these other places.

Melanomas usually have uneven edges and aren't round.

What causes it?

We're not sure what causes melanomas. Doctors think that ultraviolet (UV) rays from the sun may trigger changes in the skin cells known as melanocytes. These changes may make the cells grow in an abnormal way and cause a melanoma.

Source:
Lotze MT, Ramsey DM, Kirkwood JM, et al.
Cutaneous melanoma.
In: DeVita VT, Hellman S, Rosenberg SA (editors). Cancer: principles and practice of oncology. 6th edition. Lippincott Williams and Wilkins, London, UK; 2003.

⁷ But we don't know why this happens to some melanocytes and not to others.

There are also other kinds of skin cancer. To learn more, see Types of skin cancer.

Why me?

Some people are more likely than others to get a melanoma. Doctors call things that make you more likely to get a disease risk factors. If you have a risk factor for a disease, it doesn't mean that you will definitely get the disease. It just means that you may be more likely to get it.

The main risk factors for melanoma are having:

Source:
Lamberg L.
"Epidemic" of malignant melanoma: true increase or better detection?
Journal of the American Medical Association. 2002; 287: 2201.

Source:
National Cancer Institute.
What you need to know about skin cancer.
January 2005. Available at http://www.cancer.gov/cancertopics/wyntk/skin (accessed on 4 December 2007).

⁶

Source:
Bataille V, Grulich A, Sasieni P, et al.
The association between naevi and melanoma in populations with different levels of sun exposure: a joint case-control study of melanoma in the UK and Australia.
British Journal of Cancer. 1998; 77: 505-510.

⁸

Lots of moles on your body (more than 50 moles is a lot)
Moles with jagged edges or different colors in them
A previous melanoma
Relatives who have had melanomas
Bad sunburns when you were growing up
Fair skin
Freckles
Blond or red hair
Blue or green eyes
A job where you are exposed to chemicals such as coal tar and arsenic
A weak

immune system
The immune system is made up of the parts of the body that are devoted to fighting infection. The body is constantly being threatened by infections from things like bacteria, viruses and parasites. The immune system fights these infections in different ways. At the microscopic level, the immune system uses antibodies and white blood cells, which travel in the blood and target infectious agents, such as bacteria. These microscopic parts of the immune system either kill the infectious agent directly, or take it to other parts of the body, like the spleen, where it can be dealt with. The lymph nodes are another important part of the immune system. Within them, white blood cells filter through the foreign material that has entered the blood, to see if there are any infections. When you have a swollen gland during a cold, this is actually a lymph node that is reacting to the infection. Unfortunately, it is possible for the immune system to become confused and to use its destructive powers to target healthy parts of the body. Diseases that result from this type of situation are called autoimmune diseases.

immune system (for example, if you have

HIV
HIV stands for human immunodeficiency virus. It's the virus that causes AIDS. It makes you sick by damaging cells called CD4 cells. Your body needs these cells to fight infections. You can get HIV by sharing needles for injecting drugs ,or by having sex without a condom with someone who already has the virus.

HIV or

AIDS
AIDS stands for acquired immunodeficiency syndrome. People who are infected with the human immunodeficiency virus (HIV) get AIDS when the virus has destroyed most of their immune system. When people have AIDS, their body isn't able to fight infections. So even common infections, such as colds, can cause serious problems.

AIDS).

You will also increase your risk by going to tanning booths or using a sun lamp too often.

Sources for the information on this page:

Lamberg L."Epidemic" of malignant melanoma: true increase or better detection?Journal of the American Medical Association. 2002; 287: 2201.

Sober AJ, Koh HK, Wittenberg GP, et al.Melanoma and other skin cancers.In: Braunwald E, Hauser SL, Fauci AS, et al (editors). Harrison's principles of internal medicine. 15th edition. McGraw-Hill, New York, U.S.A.; 2001.

Martini FH, Ober WC, Garrison CW, et al.Fundamentals of anatomy and physiology.5th edition. Prentice Hall, Upper Saddle River, USA; 2001.

Cancer Research UK.Melanoma skin cancer (overview).Available at http://www.cancerresearchuk.org (accessed on 18 August 2008).

Slominski A, Wortsman J, Carlson AJ, et al.Malignant melanoma.Archives of Pathology and Laboratory Medicine. 2001; 125: 1295-1306.

National Cancer Institute.What you need to know about skin cancer.January 2005. Available at http://www.cancer.gov/cancertopics/wyntk/skin (accessed on 4 December 2007).

Lotze MT, Ramsey DM, Kirkwood JM, et al.Cutaneous melanoma.In: DeVita VT, Hellman S, Rosenberg SA (editors). Cancer: principles and practice of oncology. 6th edition. Lippincott Williams and Wilkins, London, UK; 2003.

Bataille V, Grulich A, Sasieni P, et al.The association between naevi and melanoma in populations with different levels of sun exposure: a joint case-control study of melanoma in the UK and Australia.British Journal of Cancer. 1998; 77: 505-510.

This information was last updated on Sep 01, 2008

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