Melanomas are not the commonest type of skin cancer, but probably the best known. They don’t always start as moles!
What is a malignant melanoma?
Malignant melanomas are skin growths (cancers) that have the potential to spread to other parts of the body. They can occur at any age, but are rare in childhood. They are often referred to simply as ‘melanoma’ as they are always malignant by definition.
Malignant melanomas arise from melanocytes, which are the cells that give the skin colour and are found concentrated in moles. Melanocytes occur in the skin, eye, throat and under the nail, and can therefore turn into melanomas in any of these regions
How common are malignant melanomas?
Unfortunately the incidence of malignant melanoma is increasing and now represents approximately 4% of all cancers. It is most common in Australia, where the incidence is about 45 per 100,000
What causes malignant melanoma?
There are a number of possible risk factors, which include:
Sun exposure – this seems to be the most important malignant melanoma risk factor. In particular it seems that blistering sunburn, especially during childhood, increases the risk. Short-term exposure (eg on beach holidays) appears to be more of a risk than long-term exposure (eg outdoor workers), and the sunlight risk looks set to worsen with a depletion of the protective ozone layer.
Genetic – between 5-10% of people with melanoma have a positive family history
Colour – Red hair, pale complexion and blue eyes all increase malignant melanoma risk
Skin type – skin that burns easily and tans poorly is more at risk of melanoma
Moles – malignant melanomas often grow in previously normal skin areas, but can also arise from a mole. The greater the number of moles a person has though, the higher their risk for developing melanoma.
Immunosuppression – people that have certain cancers such as lymphoma or those that are taking immunosuppression drugs (eg transplant patients) have a higher risk of malignant melanoma
What do malignant melanomas look like?
Melanomas may classically show a number of features, including the ‘ABCDE’s:
Asymmetry – the melanoma may be irregular in shape rather than rounded as for a benign mole
Border – the edge of the malignant melanoma may be irregular rather than smooth
Colour – classically, melanomas are jet black in colour although may be dark brown or of patchy colouring.
Diameter – a diameter greater than 6mm raises suspicion
Elevation – as they grow, malignant melanomas may raise and become dome-shaped
They can also have symptoms such as itching and bleeding, but often cause no pain. They do not always show these features though, and can sometimes look and act very much like a normal mole. For this reason, if you have any concerns about a skin growth, seek medical advice immediately
What is the treatment for malignant melanoma?
Generally, the first line of treatment is surgery. The growth is removed, often under local anaesthetic, and sent to a lab for investigation. If the lab believes the growth is non-cancerous, then no more surgery may be needed. If it is a melanoma, the lab will look at a number of aspects including how thick the melanoma is. Depending on the lab findings, further surgery may be needed.
Much research has been done on this issue, and at present advice says you may need a further 1cm, 2cm or even 3cm margin taken around the scar from the original surgery, depending on the thickness of the malignant melanoma. Remember that if a 1cm margin is needed, then this is 1cm all around the scar – ie leaving at least a 2cm wide wound.
With such large defects, the skin can often not be simply stitched back together. In this instance a skin graft or other procedure may be needed to close the wound
Tests for malignant melanoma
Melanomas have the potential to spread, in particular to nearby glands. Malignant melanomas on the arm will tend to spread to the armpit first, leg melanomas can spread to the groin and facial melanomas go to the neck glands. Melanomas on the back, chest or tummy area can go to any of these gland regions. For this reason, it used to be common practice to remove the nearby glands at the same time as melanoma removal. This, however, can leave significant problems such as limb swelling and is now not routinely performed except in certain select cases.
It has, however, become common to perform ‘Sentinel lymph node biopsy’. The glands are formed from a chain of lymph nodes, and the ‘sentinel node’ is the term given to the first node in the chain. If the malignant melanoma spreads to the glands, it will usually first spread to the sentinel node before moving elsewhere. A radioactive dye is injected near to the melanoma site, which travels firstly to the sentinel node. X-rays are then taken, to show the exact position of the sentinel node. This node is then surgically removed and sent to the lab. If this node is clear of tumour then no further surgery is needed as the cancer has probably not yet spread, but if tumour is found then the rest of the glands may need to be removed. Sentinel lymph node biopsy can also help indicate who might benefit from treatment with drugs such as immunotherapy.
Depending on the melanoma thickness and hospital policy, blood tests and scans (such as CT or MRI scan) may also be performed to indicate if any further spread has occurred
Where can malignant melanomas spread to?
These growths have the potential to metastasize, and as well as moving to nearby glands can also spread to other areas such as the liver, lungs, spine or brain
What happens after malignant melanoma surgery?
You will usually be followed up in clinic for up to 5 years, starting at 3 monthly intervals, extending to 6 monthly intervals. The purpose of these clinic checks is to look for any signs of the melanoma coming back (a lump in the scar, or dark growth near to the scar), and to feel the nearby glands for any hard lumps (a ‘marble-like’ lump in the gland area may indicate spread). Scans are not routinely repeated unless if there is clinical suspicion of spread
Are there any other treatment options?
Depending on the stage of your malignant melanoma, other treatment may be offered, including radiotherapy or drug therapy (including immunotherapy). These are usually given by an oncologist, who can discuss the pros and cons of each drug according to your situation
How can malignant melanoma be avoided?
Whilst the risks can never be zero, you can reduce your risks greatly with some simple steps:
Stay out of the sun, especially between 11am and 3pm, when it is most strong
Wear high factor sun cream if you need to go out in the sun (eg sports)
Re-apply sun cream regularly and especially after swimming
Wear sun-protective clothing such as long-sleeved shirts and hats
Never get sunburnt, and keep children out of the sun
This article is for information only, & does not replace the advice of a healthcare specialist. If you are concerned about any skin growth or considering treatment, you does discuss matters with your specialist