Skin cancer starts with changes in cells right at the surface of the skin. 

You might think that makes it easy to diagnose – our skin is the easiest part of us to see – but spotting cancer early is rarely simple. Many of the visual changes that could point to skin cancer are harmless, so doctors can’t confirm a diagnosis or start treatment without running extra tests. 

Today, those tests work by getting under the skin. Skin cancers are diagnosed with a biopsy, where a specialist cuts out suspicious moles or patches of skin and sends the cells on to a lab. 

As you might imagine, skin biopsies can be uncomfortable. They’re also costly, and they add to the strain on the NHS. In many cases, people sit through anxious waits only to find out they don’t have cancer. Others spend weeks on waiting lists when they should be starting treatment as soon as possible. 

But what if there was another option? What if doctors had a simple way to understand what’s happening inside skin cells without having to remove them? 

Well, Dr Sylvain Ladame and his team at Imperial College London have an idea to help with that. 

A new type of liquid biopsy

Ladame’s team have developed a skin patch that doctors could apply to suspicious skin changes to quickly check for signs of cancer. 

It’s a type of test called a liquid biopsy – with a twist.  

Usually, liquid biopsies search fluids like blood or urine for signs of cancer. But this isn’t like taking a blood sample – the best markers of skin cancer lie in tiny pockets of liquid almost on the surface of our skin. Until recently, we haven’t had tools capable of extracting this ‘interstitial fluid’ for testing. 

That changed when Ladame’s team encountered a special type of vaccine patch designed to work without an injection. Needles can be used to suck up liquid as well as inject it, they thought – so surely this could too? 

“We had to tweak it to match our research, but we instantly recognised what this technology could mean for diagnosing skin cancer,” says Ladame. “You can put the patch exactly where the changes are and monitor what’s happening in the area.”  

This wouldn’t work for most cancers, which grow inside the body rather than on its surface. Now, though, Ladame’s team believe they have a way for doctors to understand what’s causing skin changes without having to do anything invasive. 

“Today, lots of people have skin biopsies because it’s better to be safe than sorry,” Ladame says. “That’s absolutely the right thing to do, but we’re trying to reduce the stress it puts on people and the system. We want to give GPs more effective, less subjective tools to find who needs to see a dermatologist urgently.”

This new approach would also be completely painless. It could even give answers in a matter of moments. 

When a needle becomes a sponge

So, how does the skin patch work?  

Imagine a small plaster with lots of tiny needles attached to the bottom. You might be thinking, ‘Needles – wouldn’t that be painful?’ But these needles aren’t like the ones you’re probably picturing. In fact, they’re so small, and they stay so close to the surface of the skin, they don’t even reach any of our pain receptors.  

There are two reasons for that. Not only does the team want the process to be pain-free, but they also need to make sure the needles don’t draw any blood, as that could compromise the test results. 

It’s all about finding what Ladame calls the “sweet spot” – there’s a perfect balance to making sure you’re able to absorb the right liquid without causing any pain. 

“There’s actually a debate over whether the needles penetrate the skin at all,” Ladame says. “They mostly press on it, and once they’re in contact with the fluid in the skin, they can grow to three or four times their size by absorbing it.” 

That’s the other unusual thing about these needles: they work like sponges, and they can sop up everything they need in a matter of minutes. After that, the skin patch can be removed for testing. Then it’s time for the science. 

The DNA haystack 

The team are now investigating two ways of using the skin patch to check for signs of skin cancer. 

The first approach involves sending the patch to a specialist lab, where scientists can see if it has picked up any fragments of DNA released by cancer cells. That’s also what blood-based liquid biopsies are designed to find, but using interstitial fluid limits the search to a specific area, which makes the process simpler and more accurate. 

“Once these molecules from cancer cells get into the blood, it’s like looking for the proverbial needle in a haystack,” Ladame says. “Focusing on the interstitial fluid around the suspicious area means we can search a much smaller bunch of hay.”