What is a malignant melanoma?
Malignant melanomas are malignant skin growths (cancers) that have the potential to spread through 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.
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 melanoma is increasing. It 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 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). 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 melanoma risk
Skin type - skin that burns easily and tans poorly is more at risk of melanoma
Moles - melanomas often arise from previously normal skin areas, but can also arise from a mole. The greater the number of moles a person has, 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 melanoma
What do malignant melanomas look like?
Melanomas may classically show a number of features, including the 'ABCDE's:
Asymmetry - the melanoma may be iregular in shape rather than rounded as for a benign mole
Border - the edge of the 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, 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.
To see pictures of melanomas, please click here
How are malignant melanomas treated?
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 how thick the melanoma is. Depending on the thickness, 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 thickness of melanoma. Remember that if a 1cm margin is needed, then this is 1cm all around the scar - ie leaving a 2cm wide defect.
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 defect.
Are any other tests performed?
Melanomas have the potential to spread, in particular to nearby glands. 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 is, however, becoming increasingly common to perform 'Sentinel 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 melanoma spreads to the glands, it will 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 will need to be removed. This procedure is not 100% accurate, however, and while popular has not yet found favour with all surgeons.
Depending on the melanoma thickness and regional policy, blood tests and scans (such as MRI scan) may also be performed to indicate if any further spread has occurred.
Where else can melanomas spread to?
These growths have the potential to metastasize, and as well as moving to nearby glands can also spread to the liver, lungs, spine or brain.
What happens after 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?
Unfortunately, melanoma is still poorly understood. Various trials have looked at radiotherapy, chemotherapy and immunotherapy. Whilst some trials have shown promising results for certain cases, no conclusions have been made and surgery still remains one of the only treatment options.
What are the overall risks to life?
Again, this depends on tumour thickness. A patient with a thin melanoma has a greater than 90% chance of surviving 5 years. If the melanoma has spread to a lymph node, the 5 year survival drops to approximately 35%, and drops again for those with spread to other areas such as the lung. For this reason, it is very important to seek medical advice as soon as any suspicious growths are found, to hopefully remove them before they get a chance to spread.
How can 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)
Reapply 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
To see pictures of skin cancers, please click here
Other SurgeryWise articles
You may also be interested to read our articles on actinic keratosis, basal cell carcinoma, squamous cell carcinoma or moles.
The information provided is as a guide only and you should discuss matters fully with your specialist before deciding on the right procedure for you. If you have any concerns about a skin growth, seek medical advice immediately. Please also read our disclaimer