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Melanoma in situ

This page aims to provide those with a diagnosis of melanoma in situ with further information about your diagnosis and treatment options.

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. However, if you find melanoma early, treatment works well and can lead to a cure. One of the most important causes of melanoma is exposure to too much ultraviolet light in sunlight. The use of artificial sources of ultraviolet light, such as sunbeds, also increases the risk of getting a melanoma.

Melanomas often resemble moles; some develop from moles. The majority of melanomas are black or brown, but they can also be skincoloured, pink, red, purple, blue or white. About 7,000 people in the UK are diagnosed with melanoma each year. It is more common in women than men. It is a rare cancer in children, but it is the second most common cancer in people aged 15 to 34.

Although a diagnosis of melanoma can be serious, most melanomas are caught at an early stage and so do not cause any further problems. If they are not caught at the early stages then there is a higher risk of the melanoma spreading, which can reduce life expectancy.

How is it diagnosed?

If your doctor suspects that an unusual spot or mole may be a type of melanoma, it is surgically removed and sent to a pathologist. This is called a biopsy and is usually performed under local anaesthetic. A biopsy is essential for the diagnosis.

What is a melanoma in situ?

Melanoma in situ is an early stage type of melanoma. ‘In situ’ means that the cancer cells may not have had the opportunity to spread to anywhere else in the body. The cancer cells are in the top layer of the skin (the epidermis) and they are all contained in the area in which they began to develop, they have not become invasive to the lower layers of skin (dermis). If not treated, melanoma in situ can develop into an invasive cancer. It may be referred to as a ‘precancerous’ lesion.

What happens next?

Melanoma in situ is usually cured with simple surgery. The prognosis is normally excellent. It is very rare for them to come back because they were ‘in situ’, therefore they will not usually have had an opportunity to spread elsewhere in the body.

A further border of healthy tissue (about 5mm) will be taken from around the scar where the melanoma in situ was. This is second procedure is called a Wide Local Excision (WLE) and is to ensure that all cancerous cells are removed. Again, this is usually done under a local anaesthetic.


Patients may be followed up once in clinic after the completion of the WLE to provide support, information and education. Your doctor or specialist nurse should show you how to spot early skin changes in the future and how to protect yourself from UV radiation from the sun.


Cancer Research UK
Offer a wealth of information about cancer and cancer research
t: 0808 800 4040

British Association of Dermatologists
t: 0207 383 0266

Cancer information for patients and carers

Sun Smart (Cancer Research UK)
The UK’s National Skin Cancer Prevention Campaign run by Cancer Research UK.
t: 0800 226237