For seven years Sam Crook gave the mole on his back very little thought.

The freckle, no bigger than his little finger nail, was on his right shoulder blade. He was only reminded of it when, on occasion, he’d catch a glimpse of it in the mirror after a shower.

‘I was never worried about it,’ says the 39-year-old from the Wirral. ‘I had regular health checks through work, and when I mentioned the mole the doctor would reassure me that it was nothing to worry about.’

Then earlier this year, his father was diagnosed with stage four melanoma, an aggressive form of skin cancer.

‘I had previously been a bit flippant about skin cancer – I thought that it was one that was not particularly serious – but my dad’s diagnosis showed that was not the case,’ says Sam.

‘At the same time I noticed that my mole had started to change a little – rather than being like a freckle it was now darker and slightly raised.’

When this year’s work health check up rolled around, the mole was at the top of his list of concerns. Following the doctor’s initial assessment, further tests confirmed his fears: he was told he had a stage two melanoma.

Sam Crook had regular health checks through work, and when he mentioned a mole on his shoulder to his doctor, he was reassured that it was nothing to worry about

‘I was shocked, because it was not itchy or bleeding, which are the signs everyone tells you to look out for, and it had not changed that much in the couple of months before my appointment,’ he says.

‘Without my dad’s diagnosis I certainly would not have taken it as seriously and been as conscious of it as I was.’

Within two weeks Sam had the mole – and a half-inch (2cm)margin around it – removed.

At first he felt relief. But then came fear: had the cancer spread, as his father’s had?

Fortunately, he was able to get answers quickly, thanks to a newly developed test that could soon be available widely on the NHS.

Patients who are at risk of melanoma spreading are usually offered a sentinel lymph node biopsy.

The lymphatic system – a network of vessels, nodes (small, bean-shaped structures) and organs – helps defend the body against infection and disease. It collects fluid from tissues (called lymph), filters it through lymph nodes to remove pathogens and waste, and returns it to the bloodstream.

Cancer often spreads through this system first, reaching nearby lymph nodes before moving on.

To see if this has happened, surgeons remove the first lymph node that the cancer is likely to reach –the sentinel node – to test it.

If it’s clear, further surgery can often be avoided. If cancer is found, it suggests the disease may have begun to spread and additional treatment may be needed.

However, patients often wait up to four months for the procedure – partly due to shortages of the specialist dye used to identify the correct node.

‘While the data suggests this extended wait doesn’t impact outcomes, it causes huge anxiety, and we needed an alternative,’ says consultant plastic surgeon Mrs Aenone Harper-Machin, an expert in skin cancer and member of the British Association of Plastic, Reconstructive and Aesthetic Surgeons. Out of necessity, she developed a new approach.

Rather than using traditional radioactive dyes, she now uses a readily available green tracer in a procedure that takes just 15 minutes, compared to the three hours required for the standard method.

Surgeon Aenone Harper-Machin examines Sam’s lymph node using her new technique

A study presented at this year’s World Melanoma Conference found the technique was 100 per cent effective in identifying sentinel nodes in cases of head and neck cancer.

‘This is a simple procedure that is already used for breast and gynaecological cancers, so it can be rolled out very quickly now we have shown it is effective,’ says Mrs Harper-Machin. ‘And it will cut the long delays.’

Sam, who was treated at the Nuffield Hospital in Chester, was one of the first skin cancer patients to benefit. He says: ‘If I had gone down the NHS route, I would have been waiting months. I just would have been sitting stressing, worrying it had spread.

‘The new procedure meant that within two weeks I had the answer – and it was a great relief to find out it had not spread.’

Every year about 20,000 people develop melanoma – the most aggressive skin cancer – and it causes more than 2,300 deaths.

The majority of cases are caused by exposure to ultraviolet radiation, from the sun or sunbeds.

Last year rates of the cancer reached a record high in the UK, with new diagnoses increasing by almost a third in just a decade.

The main sign of the condition is a mole, either new or one that has changed size or shape. Melanomas can appear anywhere on the body but are more common in areas that are often exposed to the sun.

Mrs Harper-Machin says: ‘If you have a brown lesion or mark on your skin that is changing in size, colour or shape, the border is becoming irregular or it starts to bleed or scab over, then it should be looked at by a doctor.

‘A weakened immune system can also raise your risk.

‘And don’t let yourself be fobbed off if you’re seriously worried. On my surgical list last week were women in their 30s who’d previously been reassured by GPs.’