The first sign of a melanoma is often a new mole or a change in the appearance of an existing mole.

Normal moles are generally round or oval, with a smooth edge, and usually no bigger than 6mm in diameter.

But size is not a sure sign of melanoma. A healthy mole can be larger than 6mm in diameter, and a cancerous mole can be smaller than this.

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Anagramm / Thinkstock

See a GP as soon as possible if you notice changes in a mole, freckle or patch of skin, particularly if the changes happen over a few weeks or months.

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Scott Camazine / Alamy Stock Photo

Signs to look out for include a mole that's:

• getting bigger
• changing shape
• changing colour
• bleeding or becoming crusty
• itchy or sore

The ABCDE checklist should help you tell the difference between a normal mole and a melanoma:

• Asymmetrical – melanomas usually have 2 very different halves and are an irregular shape
• Border – melanomas usually have a notched or ragged border
• Colours – melanomas will usually be a mix of 2 or more colours
• Diameter – most melanomas are usually larger than 6mm in diameter
• Enlargement or elevation – a mole that changes size over time is more likely to be a melanoma

Melanoma can appear anywhere on your body, but they most commonly appear on the back in men and on the legs in women.

It can also develop underneath a nail, on the sole of the foot, in the mouth or in the genital area, but these types of melanoma are rare.

Melanoma of the eye

In rare cases, melanoma can develop in the eye. It develops from pigment-producing cells called melanocytes.

Eye melanoma usually affects the eyeball. The most common type is uveal or choroidal melanoma, which grows at the back of the eye.

Very rarely, it can grow on the thin layer of tissue that covers the front of the eye (the conjunctiva) or in the coloured part of the eye (the iris).

Noticing a dark spot or changes in vision can be signs of eye melanoma, although it's more likely to be diagnosed during a routine eye examination.

Read more about melanoma of the eye on our page about eye cancers.

Most skin cancer is caused by ultraviolet (UV) light damaging the DNA in skin cells. The main source of UV light is sunlight.

Sunlight contains 3 types of UV light:

• ultraviolet A (UVA)
• ultraviolet B (UVB)
• ultraviolet C (UVC)

UVC is most dangerous to the skin but is filtered out by the Earth's atmosphere. UVA and UVB damage pale skin over time, making it more likely for skin cancers to develop. UVB is thought to be the main cause of skin cancer overall, but it is not yet known whether UVA also plays a role in causing melanoma.

Artificial sources of light, such as sunlamps and tanning beds, also increase your risk of developing skin cancer.

Repeated sunburn, either by the sun or by artificial sources of light, increases the risk of melanoma in people of all ages.

Moles

You have an increased risk of melanoma if you have lots of moles on your body, particularly if they're large (more than 5mm) or unusually shaped.

For this reason, it's important to monitor your moles for changes and avoid exposing them to intense sun.

Other risk factors

You're also more likely to develop melanoma skin cancer if you have:

• a close relative who's had melanoma skin cancer
• pale skin that does not tan easily
• red or blonde hair
• blue eyes
• several freckles
• previously damaged your skin through sunburn or radiotherapy treatment
• a condition that suppresses your immune system, such as diabetes or you take medicines that suppress your immune system (immunosuppressants)
• a previous diagnosis of skin cancer

The risk of developing skin cancer also increases with age.

Cancer Research UK has more information about melanoma risks and causes.

A diagnosis of melanoma will usually begin with an examination of your skin.

Some GPs take digital photographs of a suspected tumour so they can email them to a specialist for assessment.

As melanoma is a relatively rare condition, many GPs will only see a case every few years. It's important to monitor your moles and return to your GP if you notice any changes. Taking photos to document any changes will help with diagnosis.

Seeing a specialist

You'll be referred to a dermatology clinic for further testing if melanoma is suspected. You should see a specialist within 2 weeks of seeing your GP.

A skin specialist (dermatologist) or plastic surgeon will examine the mole and the rest of your skin. They may remove the mole and send it for testing (biopsy) to check whether it's cancerous. A biopsy is usually done using local anaesthetic to numb the area around the mole, so you will not feel any pain.

If cancer is confirmed, you'll usually need another operation, most often done by a plastic surgeon, to remove a wider area of skin. This is to make absolutely sure that no cancerous cells are left behind in the skin.

Further tests

You'll have further tests if there's a concern that the cancer has spread into other organs, bones or your blood.

Sentinel lymph node biopsy

If melanoma spreads, it will usually begin spreading through channels in the skin (lymphatics) to the nearest group of glands (lymph nodes). Lymph nodes are part of the body's immune system. They help remove unwanted bacteria and particles from the body and play a role in activating the immune system.

A sentinel lymph node biopsy is a test to determine whether microscopic amounts of melanoma (less than would show on any X-ray or scan) have spread to your lymph nodes. It's usually done by a specialist plastic surgeon, while you're under general anaesthetic.

A combination of blue dye and a weak radioactive chemical is injected around your scar. This is usually done just before the wider area of skin is removed. The solution follows the same channels in the skin as any melanoma.

The first lymph node the dye and chemical reaches is known as the "sentinel" lymph node. The surgeon can locate and remove the sentinel node, leaving the others intact. The node is then examined for microscopic specks of melanoma (this process can take several weeks).

If the sentinel lymph node is clear of melanoma, it's extremely unlikely that any other lymph nodes are affected. This can be reassuring, because if melanoma reaches the lymph nodes, it's more likely to spread elsewhere.

If the sentinel lymph node contains melanoma, there's a risk that other lymph nodes in the same group will also contain melanoma.

Your surgeon should discuss the pros and cons of having a sentinel lymph node biopsy before you agree to having it. 

Lymph node dissection or completion lymphadenectomy

An operation to remove the remaining lymph nodes in the group is known as a completion lymph node dissection or completion lymphadenectomy. Again, you should discuss the pros and cons of the procedure with your surgeon.

Other tests you may have include:

• a CT scan
• a MRI scan
• a positron emission tomography (PET) scan
• blood tests

Cancer Research UK has more information about test to diagnose melanoma and tests to stage melanoma.

Melanoma stages

Healthcare professionals use a staging system called the AJCC system to describe how far melanoma has grown into the skin (the thickness) and whether it has spread. The type of treatment you receive will depend on what stage the melanoma has reached.

Melanoma stages are described as:

• Stage 0 – the melanoma is on the surface of the skin
• Stage 1A – the melanoma is less than 1mm thick
• Stage 1B – the melanoma is 1mm to 2mm thick, or less than 1mm thick and the surface of the skin is broken (ulcerated) or its cells are dividing faster than usual
• Stage 2A – the melanoma is 2mm to 4mm thick, or it's 1mm to 2mm thick and ulcerated
• Stage 2B – the melanoma is thicker than 4mm, or it's 2mm to 4mm thick and ulcerated
• Stage 2C – the melanoma is thicker than 4mm and ulcerated
• Stage 3A – the melanoma has spread into 1 to 3 nearby lymph nodes, but they're not enlarged; the melanoma is not ulcerated and has not spread further
• Stage 3B – the melanoma is ulcerated and has spread into 1 to 3 nearby lymph nodes but they're not enlarged, or the melanoma is not ulcerated and has spread into 1 to 3 nearby lymph nodes and they are enlarged, or the melanoma has spread to small areas of skin or lymphatic channels, but not to nearby lymph nodes
• Stage 3C – the melanoma is ulcerated and has spread into 1 to 3 nearby lymph nodes and they're enlarged, or it's spread into 4 or more nearby lymph nodes
• Stage 4 – the melanoma cells have spread to other parts of the body, such as the lungs, brain or other areas of the skin

Cancer Research UK has more information about the stages of melanoma.

Surgery is the main treatment for melanoma.

If you have melanoma skin cancer you'll be cared for by a team of specialists that should include a skin specialist (dermatologist), a plastic surgeon, a specialist in radiotherapy and chemotherapy (oncologist), an expert in tissue diseases (pathologist) and a specialist nurse.

When helping you decide on your treatment, the team will consider:

• the type of cancer you have
• the stage of the cancer (its size and how far it has spread)
• your general health

Your treatment team will recommend what they believe to be the best treatment option, but the final decision will be yours.

Before going to hospital to discuss your treatment options, you may find it useful to write a list of questions to ask the specialist.

For example, you may want to find out about the advantages and disadvantages of particular treatments.

Read more about questions to ask your doctor.

Treating stage 1 to 2 melanoma

Treating stage 1 melanoma involves surgery to remove the melanoma and a small area of skin around it. This is known as surgical excision.

Surgical excision is usually done using local anaesthetic, which means you'll be awake, but the area around the melanoma will be numbed, so you will not feel pain. In some cases, general anaesthetic is used, which means you'll be unconscious during the procedure.

If a surgical excision is likely to leave a significant scar, it may be done in combination with a skin graft. However, skin flaps are now more commonly used because the scars are usually less noticeable than those resulting from a skin graft.

Read more about flap surgery.

In most cases, once the melanoma has been removed there's little possibility of it returning and no further treatment should be needed. Most people (80 to 90%) are monitored for 1 to 5 years and are then discharged with no further problems.

Sentinel lymph node biopsy

A sentinel lymph node biopsy is a procedure to test for the spread of cancer.

It may be offered to people with stage 1B to 2C melanoma. It's done at the same time as surgical excision.

You'll decide with your doctor whether to have a sentinel lymph node biopsy.

If you decide to have the procedure and the results show no spread to nearby lymph nodes, it's unlikely you'll have further problems with this melanoma.

If the results confirm melanoma has spread to nearby nodes, your specialist will discuss with you whether further surgery is required.

Additional surgery involves removing the remaining nodes, which is known as a lymph node dissection or completion lymphadenectomy.

Treating stage 3 melanoma

If the melanoma has spread to nearby lymph nodes (stage 3 melanoma), further surgery may be needed to remove them.

Stage 3 melanoma may be diagnosed by a sentinel node biopsy, or you or a member of your treatment team may have felt a lump in your lymph nodes.

The diagnosis of melanoma is usually confirmed using a needle biopsy (fine needle aspiration).

Removing the affected lymph nodes is done under general anaesthetic.

The procedure, called a lymph node dissection, can disrupt the lymphatic system, leading to a build-up of fluids in your limbs. This is known as lymphoedema.

Cancer Research UK has more information about surgery to remove lymph nodes.

Treating stage 4 melanoma

If melanoma comes back or spreads to other organs it's called stage 4 melanoma.

In the past, cure from stage 4 melanoma was very rare but new treatments, such as immunotherapy and targeted treatments, show encouraging results.

Treatment for stage 4 melanoma is given in the hope that it can slow the cancer's growth, reduce symptoms, and extend life expectancy.

You may be offered surgery to remove other melanomas that have grown away from the original site. You may also be able to have other treatments to help with your symptoms, such as radiotherapy and medicine.

If you have advanced melanoma, you may decide not to have treatment if it's unlikely to significantly extend your life expectancy, or if you do not have symptoms that cause pain or discomfort.

It's entirely your decision and your treatment team will respect it. If you decide not to receive treatment, pain relief and nursing care will be made available when you need it. This is called palliative care.

Immunotherapy

Immunotherapy is used to treat advanced (stage 4) melanoma, and it's sometimes offered to people with stage 3 melanoma as part of a clinical trial.

Immunotherapy uses medicine to help the body's immune system find and kill melanoma cells.

Several different medicines are available, some of which can be used on their own (monotherapy) or together (combination therapy).

Medicines used include:

• ipilimumab
• nivolumab
• pembrolizumab
• talimogene laherparepvec

These medicines are often recommended for people with previously treated or untreated advanced melanoma that's spread or cannot be removed using surgery.

They are given either via a drip or by injection every few weeks. Some medicines are given on a short-term basis over a few weeks. Others are given on a longer-term basis.

Side effects of immunotherapy medicines include:

• diarrhoea
• rash
• itching
• fatigue
• feeling and being sick
• decreased appetite
• tummy (abdominal) pain

Targeted treatments

Around 1 in 2 people with melanoma have a change (mutation) in a gene called BRAF. This mutation causes cells to grow and divide too quickly .

Targeted medicine can be used to target this mutation to slow or stop cancer cells growing.

Targeted treatments for melanoma include:

• vemurafenib
• dabrafenib
• trametinib

These medicines may be recommended as a treatment for people who have the gene mutation and have an aggressive type of melanoma in 1 part of their body or melanoma that's spread.

The side effects of these medicines can include:

• decreased appetite
• headache
• cough
• feeling and being sick
• diarrhoea
• rash
• hair loss or thinning

Cancer Research UK has more information on immunotherapy and targeted treatments for melanoma.

Radiotherapy and chemotherapy

You may have radiotherapy after an operation to remove your lymph nodes, and it can also be used to help relieve the symptoms of advanced melanoma. Controlled doses of radiation are used to kill the cancerous cells.

If you have advanced melanoma, you may have a single treatment or a few treatments. Radiotherapy after surgery usually consists of a course of 5 treatments a week (1 each day from Monday to Friday) for several weeks. There's a rest period over the weekend.

Common side effects associated with radiotherapy include:

• tiredness
• feeling sick
• loss of appetite
• hair loss
• sore skin

Many side effects can be prevented or controlled with prescription medicines, so tell your treatment team if you experience any. The side effects of radiotherapy should gradually reduce once treatment has finished.

Chemotherapy is now rarely used to treat melanoma. Targeted treatments and immunotherapy are the preferred treatment options.

Melanoma vaccines

Research is under way to produce vaccines for melanoma, either to treat advanced melanoma or to be used after surgery in people with a high risk of the melanoma returning.

They're currently only given as part of a clinical trial.

Cancer Research UK has more information about melanoma vaccines.

Follow-up

After your treatment, you'll have regular follow-up appointments to check whether:

• there are signs of the melanoma coming back
• the melanoma has spread to your lymph nodes or other areas of your body
• there are signs of any new primary melanomas

Your doctor or nurse will examine you. They'll ask about your general health and whether you have any questions or concerns.

You may be offered treatments, such as immunotherapy, to try to prevent the melanoma returning. This is called adjuvant treatment.

There's not much evidence that adjuvant treatment helps prevent melanoma coming back, so it's currently only offered as part of a clinical trial.

There's evidence that checkpoint therapies, which boost the body's immune responses to cancer, may be used in the future if clinical trials provide evidence that they're effective.

Cancer Research UK has more information about follow-up appointments.

Help and support

Being diagnosed with melanoma can be difficult to deal with. You may feel shocked, upset, numb, frightened, uncertain and confused. These types of feelings are natural.

You can ask your treatment team about anything you're unsure about.

Your family and friends can be a great source of support. Talking about cancer and how you're feeling can help both you and members of your family cope with the situation.

Some people prefer to talk to people outside their family. There are several UK-based charities that have specially trained staff you can speak to on a free helpline:

• Cancer Research UK – call 0808 800 4040 (Monday to Friday, 9am to 5pm)
• Macmillan Cancer Support – call 0808 808 0000 (every day, 8am to 8pm)
• Melanoma UK – 0808 171 2455 or you can use its online form

Cancer Research UK also has a section about living with melanoma.

Find more cancer support services near you.

Clinical trials

Any new cancer treatment is first given to patients in a clinical trial.

A clinical trial is a rigorous way of testing new treatments on people. Patients are closely monitored for any effects the medicine has on the cancer as well as any side effects.

Many people with melanoma are offered entry into clinical trials.

If you're asked to take part in a clinical trial, you'll be given an information sheet, and if you decide to take part you'll be asked to sign a consent form.

You can withdraw from a clinical trial at any time without it affecting your care.