Cutaneous melanoma: signs, diagnosis and treatment

Skin colour comes from melanin, which is made by cells called melanocytes. Melanoma develops when those cells grow and divide faster than they should. NHS inform explains that UV radiation from sunlight, sunbeds or sunlamps can build up and damage the DNA inside melanocytes, which is how this change begins.

Melanoma can start in an existing mole or in skin that looked normal beforehand. The NHS notes that it can appear anywhere on the body but is more common in areas that are often exposed to the sun, and that some rarer types affect the eyes, the soles of the feet, the palms of the hands or the genitals.

NHS inform reports that about 16,700 people are diagnosed with melanoma in the UK each year and that the number is rising. It becomes more common with age, yet it is also seen in people in their teens and twenties more often than some other cancers.

Doctors group skin melanoma into types according to how it grows. The table below follows the four main types described by NHS inform. Knowing the type helps explain why a melanoma on the back looks different from one under a toenail.

The NHS describes normal moles as usually round with smooth edges, one colour and about the size of a pencil end or smaller. Melanomas often differ in several ways: an uneven shape or edge, two differently shaped halves, a mix of two or more colours, and a larger width, often more than 6mm, although the NHS adds that early ones can be smaller.

A mole that changes over time is the point most worth acting on. Swelling, soreness, bleeding, itching and crusting are further signs the NHS lists. NHS inform suggests taking a photograph of anything unusual so you can compare it later, and notes that many other skin conditions are not cancer, especially in older people.

• A mole that has changed size, shape or colour.

• A mole that is painful, itchy, inflamed, bleeding or crusty.

• A new or unusual mark that has not gone away after a few weeks, including on the palms or soles.

• A dark area under a nail that was not caused by an injury.

Beyond UV exposure, the NHS lists several features that raise the chance of melanoma: pale skin that burns easily, red or blonde hair, blue or green eyes, many freckles or moles, a history of sunburn or heavy sun exposure, regular sunbed use, and a personal or family history of skin cancer.

People with black or brown skin have a lower chance of melanoma but can still develop it. The NHS says it most often shows up on the soles of the feet, palms of the hands or under a nail in this group, so checking those areas matters.

For prevention the NHS advises staying out of the sun in the hottest part of the day (11am to 3pm in the UK), covering arms and legs, wearing a wide-brimmed hat and sunglasses with UV protection, using sunscreen of at least SPF 30 with at least 4-star UVA protection and reapplying it, and taking particular care to protect babies and children.

The route usually begins with a GP, who asks about your health, family history and the skin change, then looks at the mole. The NHS says the GP may photograph it and send the image to a dermatologist, which is called teledermatology. If cancer is possible you may be given an urgent referral; the NHS stresses this does not definitely mean you have cancer. NHS inform says you should be seen at hospital within 2 weeks after such a referral.

At the hospital the dermatologist examines your skin, often with a magnifying device called a dermatoscope. A mole that is suspicious will normally be cut out with a small area of surrounding skin, an excision biopsy, so a laboratory can examine it. NHS inform adds that an unusual mole which does not look suspicious enough to remove may instead be checked regularly, sometimes with photographs.

If melanoma is confirmed, further tests may follow. The NHS lists CT or MRI scans, tests of the lymph nodes and blood tests. NHS inform describes a sentinel lymph node biopsy, which checks the lymph nodes nearest the melanoma, and says not everyone needs lymph node tests because it depends on how deep the melanoma is and whether the nodes feel or look swollen. The results give the stage, meaning how deep the cancer is and how far it has spread, which guides treatment. Some melanomas are also tested for gene changes, because that result affects which targeted or immunotherapy medicines might work.

A team of specialists, the multidisciplinary team, discusses each person's case. The NHS says treatment depends on where the cancer is, whether it has spread and your general health, and that surgery is the main treatment, particularly when melanoma is found early.

After the biopsy, most people have a further operation called a wide local excision to remove more tissue around the site, aiming to take away all cancer cells. NHS inform says that for early melanoma, confined to the skin, this is often the only treatment needed. If the melanoma is on a visible area such as the face, a plastic surgeon may operate, and a skin graft may be used when a large area is removed.

Other treatments depend on the situation. The NHS explains that radiotherapy is sometimes used to shrink large melanomas and relieve symptoms, that targeted medicines or immunotherapy are used for melanomas that cannot be treated with surgery or that have spread, and that chemotherapy is sometimes used for advanced melanoma but does not work as well as those newer options. NHS inform also describes adjuvant treatment, extra treatment after surgery for up to 12 months in some cases, to reduce the chance of the melanoma returning; your specialist weighs the benefits against the side effects.

NHS inform says follow-up depends on the stage. After removal of a stage 0 melanoma (melanoma in situ) you may need only one follow-up appointment, whereas other stages mean regular appointments over several years, and some people are offered scans. At these visits the doctor or nurse examines your skin, scar and nearby lymph nodes, and may photograph or measure moles.

Because the chance of a second melanoma is higher, NHS inform recommends checking your own skin at least once a month, using a mirror or a helper for areas you cannot see, and continuing sun protection. It also says there is a better chance of a cure if another melanoma is found early.

Anyone worried about a mole should see their GP first, and the NHS route to a dermatologist is free at the point of use. Some people choose to see a private consultant dermatologist, for example to be seen sooner or to have a mole examined with dermoscopy in a private clinic. A private route does not change the underlying steps: examination, excision biopsy if needed, laboratory report, staging and discussion by a specialist team.

If you do go privately, it is sensible to ask who will review the pathology result, whether a multidisciplinary team will discuss a confirmed melanoma, and how follow-up will be organised, so that nothing is lost between private and NHS care. The NHS says a clinical nurse specialist is normally your main point of contact during and after treatment.