Melanoma: causes, identification and diagnosis

The British broadcaster and DJ, Chris Evans, has revealed that he has been diagnosed with a skin cancer called a “melanoma”. The 57-year-old says that he was tested for the disease after his masseuse noticed a mark on his shin. So, what exactly is melanoma? Julia Newton-Bishop is a professor of dermatology at the University of Leeds…

Julia - Melanoma is a cancer of the cells in our skin that produce our skin colour. Most melanomas occur on some exposed skin.

Chris - And who tends to get them?

Julia - It occurs when genetic damage happens within the cell by exposure essentially to the sun. Within the sun's rays, there are shorter wavelengths called UVB, and these are important to us because they allow us to make vitamin D, but they also damage skin. And people who are vulnerable to melanoma have on the whole pale skin and they have the sort of skin that easily burns. So the people who are most at risk are those with the pale skin, often with red hair. And it's all about burning because it's during that process of sunburn that this genetic damage occurs, which later causes melanoma.

Chris - What about other sources of ultraviolet? People who go to tanning salons, for example.

Julia - It is well described now that excessive exposure to UVA in sun beds puts you at increased risk of melanoma. But I wouldn't want to give the impression that everyone's safe so long as they don't use a sunbed, because most melanoma occurs in people who get burnt in the garden on a lovely day like this, when they're outside. Especially if they're sunbathing.

Chris - Chris Evans is in his mid fifties. Is that the peak age or is he late to the party for melanoma?

Julia - 50 used to be about the average age for melanoma. It's a bit higher now, but it's not rare to see very young people in their twenties and thirties.

Chris - And what should a person look out for?

Julia - Half of melanomas occur in moles, as a changing mole. So I'm looking at my arms now, moles are usually quite circular. They grow to a certain diameter and then they stop growing - well-behaved moles. In a melanoma, you get a mole that's growing erratically and tends to be irregular in shape and irregular in colour, so a changing mole. Getting checked early is the important thing because if you have a melanoma on your skin and it's removed very early, then they don't come back. You've got it cured.

Chris - So if a person has something that they think might fulfil some of those criteria, how should it be investigated and what would be the likely outcome for the patient?

Julia - Clinical diagnosis gives you a very strong clue, and dermatologists are usually about 70 or 80% right. The norm is to then remove it surgically to cut the whole thing out with a narrow margin of normal skin at the edge, done with a local anaesthetic. And then that bit of skin goes off to the laboratory and the pathologist looks at that tissue under a microscope and looks for characteristic changes that tell us that this is a melanoma. Sometimes that's absolutely all that needs to be done. And for those in whom we feel we need to take a little bit more just to be sure, the patient would go back and have more skin removed from the edge just to be sure that we've removed all those cells. For many patients, a proportion of patients in whom the melanoma is a bit thicker, then they might consider having an optional operation on top of that, or the Sentinel Node Biopsy, which is a way of looking for cancer cells that have escaped the skin and are in the lymphatic drainage system. But essentially, the overwhelming majority of patients, 80%, are cured by that first surgery. And nothing more needs to be done.