Melanoma is the most serious type of skin cancer. It affects young adults as well as older people. If diagnosed at an early stage, before it has spread, treatment is likely to be curative. The outlook is not so good if it has spread before being treated. See your doctor if you develop an abnormal patch of skin or a change in appearance of a mole.
The skin has two layers - the epidermis and the dermis. Beneath the dermis is a layer of fat, and then the deeper structures such as muscles and tendons.
The epidermis has three main types of cell:
Cancer is a disease of the cells in the body. The body is made up from millions of tiny cells. There are many different types of cell in the body, and there are many different types of cancer which arise from different types of cell. What all types of cancer have in common is that the cancer cells are abnormal and multiply out of control.
Skin cancer is the most common cancer in the UK. Around 100,000 cases are diagnosed each year in the UK. Skin cancers are divided into:
A malignant tumour is a lump or growth of tissue made up from cancer cells which continue to multiply. Malignant tumours invade into nearby tissues and organs, which can cause damage.
Malignant tumours may also spread to other parts of the body. This happens if some cells break off from the first (primary) tumour and are carried in the bloodstream or lymph channels to other parts of the body. These small groups of cells may then multiply to form secondary tumours (metastases) in one or more parts of the body. These secondary tumours may then grow, invade and damage nearby tissues, and spread again.
The rest of this leaflet is just about melanoma. See separate leaflet called Skin Cancer - Non-melanoma for further detail on non-melanoma skin cancer.
Melanoma is the least common form of skin cancer, but it is the most serious. It is the one most likely to spread to other parts of the body. There are about 9,000 new cases of melanoma each year in the UK. The number of cases has about doubled over a period of 20 years or so. Melanoma is the second most common cancer in people aged 15-34.
A cancerous tumour starts from one abnormal cell. The exact reason why a cell becomes cancerous is unclear. It is thought that something damages or alters certain genes in the cell. This makes the cell abnormal and multiply out of control. (See separate leaflet called Cancer - What Causes Cancer for more details.)
The main risk factor which damages skin and can lead to a melanoma is damage from the sun. It is the ultraviolet (UV) radiation in the sunshine and in sunbeds which does the damage. About 6 in 10 cases of melanoma are thought to be caused by UV damage. UV light damages the DNA (genetic material) in your skin cells which can then lead to skin cancers developing.
People most at risk to UV skin damage are people with fair skin - in particular, those with skin which always burns and never tans, red or blond hair, green or blue eyes. Melanoma is uncommon in dark-skinned people, as they have more protective melatonin in their skin.
Children's skin is most vulnerable to damage. Sun exposure in childhood is the most damaging. People who had a lot of freckling in childhood, or had frequent or severe sunburn in childhood, are most at risk of developing melanoma as adults. (The damage to the skin can occur many years before a cancer actually develops.)
Melanoma is most common in fair-skinned people who live in hot countries nearer to the equator. Australia and Israel have the highest rates. The rate in the USA is quite high, but decreases the further north you go in the country.
Other factors which increase the risk of developing melanoma include the following:
See DermNet NZ for pictures of different melanomas: http://dermnetnz.org/lesions/melanoma.html
A typical melanoma starts as a small dark patch on the skin. It can develop from a normal part of skin, or from an existing mole. A melanoma is often different to a mole in one or more of the following ways (summed up as ABCDE) - that is:
However, some melanomas are not dark, and some melanomas are not typical in how they look. As a melanoma grows in the skin, it may itch, bleed, crust or ulcerate.
The take home message is: see a doctor if you develop a lump or patch on the skin, which you are unsure about, or if a mole changes in its shape, border, colour or size.
A melanoma can develop on any area of skin. The most common place for a melanoma to develop in a woman is on the legs; whereas for men it is on the chest or back. Rarely, a melanoma can develop in the iris or back of the eye. (Unlike non-melanoma skin cancers, melanomas can develop on areas of skin not often exposed to the sun. These areas may have had short spells of sun damage such as during a holiday.)
If some cells break off and spread (metastasise) to other parts of the body, various other symptoms can develop. A common early symptom of spread is for the nearby lymph glands (nodes) to swell.
If a melanoma is suspected then your doctor is likely to advise an excisional biopsy. This is where the entire abnormal area of skin is removed by a minor operation. (Local anaesthetic is injected into the skin to make this painless.) This tissue is looked at under the microscope. This is to:
When doing an excisional biopsy (described above) the doctor will remove a margin of normal skin around the melanoma. When the biopsy is looked at under the microscope, if the doctor is sure that all the melanoma cells have been removed, and the melanoma cells are confined to the top layer of skin, then no further treatment may be needed. Otherwise, a second operation called a wide local excision is usually advised.
This aims to remove an area of normal skin around where the melanoma had been (before it was removed with excisional biopsy). This aims to make sure that any cells which may have grown in the local area of skin have been removed. The amount of normal looking skin removed varies - depending on the thickness of the melanoma (how deep it has spread into the skin) as reported from the biopsy. It may be 1-2 cm around where the melanoma had been. This operation may be done under local or general anaesthetic. In some cases a skin graft may be needed to cover the wound.
The aim of staging is to find out how much a cancer has grown and spread. Finding out the stage of the cancer helps doctors to advise on the best treatment options. It also gives a reasonable indication of outlook (prognosis). (See separate leaflet called Staging and Grading Cancer for further details).
Most cases of melanoma are diagnosed at stage one when there is a very good chance that treatment will cure the condition. Other stages (2-4) are diagnosed if the tumour has spread. The stage diagnosed depends on how much and how far the the original tumour has spread to other parts of the body.
If the initial biopsy and the tissue taken from the wide local excision show that the melanoma is just in the top layer of skin and is less than 0.76 mm thick, then no further tests are usually needed. It is highly unlikely that it will have spread. This is an early stage 1 melanoma.
A doctor will examine you to see if you have any swollen lymph nodes (glands) near to the melanoma. If you have, then the melanoma may have spread to these local lymph nodes.
It is possible that there may be some early spread without causing symptoms if the melanoma is thicker than 0.76 mm on the initial biopsy. In particular, there may be spread of some cells to the nearest lymph node without it yet causing it to swell. Therefore, a test called sentinel node biopsy, and sometimes other tests, may be advised.
Sentinel node biopsy. This is a relatively new test which may be considered. In this test, a small sample of the nearest lymph node is taken as an additional procedure when the melanoma is being removed. However, sentinel node biopsy is not used routinely, and is usually performed only as part of a research study. This means that it is not an essential part of treatment.
Other tests. Tests which may be advised depend on: whether you have symptoms; whether the lymph nodes are found to be involved; the thickness of the primary melanoma (the thicker the primary tumour, the greater the chance of spread). The tests aim to detect if the cancer has spread to other parts of the body. For example, you may be advised to have X-rays, blood tests, scans, etc.
The treatment depends on the stage. Generally, if the melanoma is thin then a small operation to cut out the tumour (the biopsy or wide local excision described above) is usually all the treatment that is needed. This is likely to clear all the cancer cells. Following the treatment you will usually be seen at regular intervals.
If the melanoma is deeper then you may need a larger operation which may include removing the local lymph nodes. You may also be given additional treatment, depending on where the cancer has spread to and what symptoms you have. This may include:
The prognosis for people with malignant melanomas has been improving over a period of 25 years and people with melanomas now have amongst the best outlook for any cancer. Around three quarters of people who have a melanoma removed will have no further problems.
The outlook depends on the stage. Most cases of stage 1 melanoma are cured with a minor surgical operation to remove the tumour (described above). For people with deeper melanomas then there is still a chance of cure. People with advanced melanoma that has spread to other parts of the body are not likely to be cured, but treatment can often slow down the progression of the cancer.
The treatment of cancer is a developing area of medicine. New treatments continue to be developed and the information on outlook above is very general. The specialist who knows your case can give more accurate information about your particular outlook, and how well your type and stage of cancer is likely to respond to treatment.
Most skin cancers (non-melanoma and melanoma skin cancers) are caused by excessive exposure to the sun. We should all limit our sun exposure in the summer months (or all year when in hot countries nearer the equator) by:
In particular, children should be protected from the sun. Sunburn or excessive exposure to the sun in childhood is thought to be the biggest risk factor to the developing of skin cancer as an adult. Also, people with a family history of melanoma should take extra care to protect their skin from the sun.
See separate leaflet called Preventing Skin Cancer for details.
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