Skin cancer 101: what everyone should know

By Tim Gunn

A microscope image showing layers of healthy skin. Jose Luis Calvo/Shutterstock.com

All the wonders of your body are wrapped up in your skin. It’s the biggest organ, the most protective, and the one that connects us to the world outside.

This article can’t be quite that comprehensive, but our work on skin cancer is getting close. Over the last 50 years, we’ve helped double survival for melanoma, the most serious type of skin cancer. Now, 9 in 10 people diagnosed with melanoma in the UK will survive 10 years or more.

And we’re not done yet. We want to bring about a world where everybody lives longer, better lives, free from the fear of skin cancer – no matter who they are or where they’re from.

This is another step on that journey. Here, we’re answering some of the biggest questions about skin cancer and sharing the most important things you need to know. We’re also exploring some of the work we’re doing to keep making life-saving, life-improving progress for people affected by the disease.

What is skin cancer?

Cancer is when abnormal cells divide in an uncontrolled way. Skin cancer is any type of cancer that starts on the outer layers of our skin.

But our skin isn’t all one thing. It’s made up of different cells working together. Depending on the type of cells they start in, skin cancers have different names and behave in different ways.

The biggest difference is the one that separates melanoma skin cancers, which start in the cells that give skin its colour (melanocytes), from non-melanoma skin cancers, which usually start in the cells that make skin an effective barrier (keratinocytes).

1. Non-melanoma skin cancers

The main types of non-melanoma skin cancer are basal cell carcinoma and squamous cell carcinoma. We don’t tend to talk about them as much as melanoma skin cancers. In fact, non-melanoma skin cancers are usually left out of cancer statistics. They're more common than any other cancer type, but they grow very slowly and rarely spread (metastasise). That means they’re much easier to treat and cure, usually with a minor operation, and very unlikely to have any long-term impact on your health.

A cell from a squamous cell carcinoma seen through a microscope.

A cell from a squamous cell carcinoma. Photo by: Annie Cavanagh

2. Melanoma skin cancers

Melanoma skin cancer is rarer than non-melanoma skin cancer, but it's still the fifth most common cancer type in the UK. Melanomas grow more quickly and are more likely to metastasise. As a result, they're usually more serious.

The 3D structure of a melanoma cell. Picture by National Cancer Institute on Unsplash

What causes skin cancer?

Skin cancer is usually caused by overexposure to ultraviolet (UV) rays from the sun.

Our scientists were the first people to prove that link almost 100 years ago. Today, with the number of skin cancer cases rising, it's more relevant than ever. Up to 9 in 10 melanoma cases in the UK could be prevented by staying safe in the sun and avoiding sunbeds.

Holidaymakers enjoying the summer sun on the beach in Llandudno, Wales, in the 1920s, around the time our scientists proved the link between UV radiation and skin cancer. Summer outfits have changed since then. Photo from UK Photo & Social History Archive

Holidaymakers enjoying the summer sun on the beach in Llandudno, Wales, in the 1920s, around the time our scientists proved the link between UV radiation and skin cancer. Summer outfits have changed since then. Photo from UK Photo & Social History Archive

Those cases – and most cases of non-melanoma skin cancer – happen because too much UV radiation can damage the DNA in our skin cells.

That’s a problem because our DNA is a sort of living instruction manual. It tells each of our cells how to function and keeps them working in harmony. If lots of DNA damage builds up over time, it can lead to faults that make cells malfunction and grow out of control.

Sunburn is a clear sign of DNA damage in your skin, so it can raise the risk of skin cancer. In general, if you have lighter skin and tend to burn in the sun, you’re more at risk of skin cancer than if your skin is naturally darker. Still, people of all skin tones can get skin cancer, so it’s important for everyone to think about protecting their skin when the sun is strong.

A sunburn doesn’t have to be raw, peeling or blistering. For people with darker skin tones, your skin may feel irritated, tender or itchy. For people with lighter skin tones, it may also go pink or red in the sun. Getting sunburnt once doesn’t mean you will definitely get skin cancer, but the more times you get sunburnt the higher your risk.

More rarely, DNA damage leading to skin cancer can happen for other reasons. For example, acral melanomas, which start in the palms of the hands, soles of the feet and under the nails, aren’t related to exposure to the sun. They're more commonly diagnosed in people with brown or black skin.

Research spotlight: How does cancer develop?

Interestingly, scientists have discovered that cells with faults in their DNA also exist in our healthy skin. That suggests these faults alone aren’t enough to cause cancer. Until something else changes, the skin cells can keep functioning normally.

With our funding, Dr Yi Feng at the University of Edinburgh is using advanced lab techniques and imaging to study what else happens to trigger skin cells to become cancerous.

This work could improve our understanding of how skin and other cancers develop, potentially leading to new prevention strategies and treatments.

How can we prevent skin cancer?

You can still enjoy the sun while protecting yourself from skin cancer. We've teamed up with NIVEA Sun to recommend the three key steps you can take to reduce your risk:

Spend time in the shade: take extra care between 11am and 3pm in the UK, when the sun’s UV rays are at their strongest.
Cover up with clothes: wear a wide brimmed hat, UV protection sunglasses and looser clothing that covers your shoulders.
Apply sunscreen: regularly and generously use a sunscreen that is at least SPF 30 and 4 or 5 stars. Remember to reapply sunscreen regularly throughout the day, including ‘once a day’ and ‘water resistant’ products.

It’s important to use all three steps together – even if it's cloudy or cool outside. The sun can be strong enough in the UK to damage your skin from mid-March to mid-October, and over 90% of UV rays can pass through cloud and cause sunburn.

If you want to be sure about your risk of sunburn, you can check the current UV levels on your phone’s weather app. The higher the number, the greater the risk.

The other important thing to do is stay away from sunbeds, which emit high intensity UV radiation. They do that to give people a tan more quickly, but a suntan can actually be another sign of skin damage.

Our skin tans to protect itself when it starts getting too much UV radiation. When the DNA damage starts, melanocytes create more melanin, the pigment that gives our skin its colour. Skin cells then take up that melanin to try and protect themselves, but there’s only so much they can do. That’s why we say there’s no such thing as safe tanning.

Our impact: Changing the law around sunbeds

We helped fund the landmark research from the International Agency for Research on Cancer that confirmed the association between tanning beds and melanoma in 2007. It showed that the risk of melanoma was especially high in people who used sunbeds before the age of 35.

After that, we began campaigning to restrict sunbed use to over-18s. Our work led directly to the Sunbed Regulation Act, which was passed in 2010. It’s now illegal for UK businesses to let anyone under 18 use a sunbed.

Aigneis/Shutterstock.com

Who gets skin cancer?

As we’ve discussed, anyone can get skin cancer, but it becomes more common as people get older. That’s because the DNA damage that can lead to cancer usually builds up over time.

Each year, around 5 in 10 new cases of non-melanoma skin cancer in the UK are diagnosed in people aged 75 and over. For melanoma skin cancer, this is 3 in 10 cases.

However, melanoma skin cancer also occurs relatively frequently at younger ages. This is largely due to the effects of UV radiation on growing cells, and shows why it’s so important for young people to stay safe in the sun and avoid sunbeds.

Some people also have a higher-than-average risk of skin cancer. These include people with a family history of skin cancer, people with a weakened immune system and people who have already had skin cancer. The work we’ve done and are doing to understand and detect skin cancers is especially helpful for these groups.

Bright red burn damage visible on squamous skin cells through a microscope.

Burn damage to squamous skin cells. Photo by Anne Weston, Francis Crick Institute

Research spotlight: Cancer risk and early detection

In 2002, our researchers found that people can inherit certain DNA changes that increase their risk of developing melanoma. Thanks to that discovery, people with a higher risk of skin cancer can take extra steps to protect themselves, including going for regular skin checks from a specialist.

Today, we’re also funding research that could help spot whether melanoma skin cancers might be coming back after treatment.

In our DETECTION-2 trial, researchers are investigating a blood test with the potential to spot signs of a returning melanoma before it causes any symptoms. The research will help us find out if this type of test, also known as a liquid biopsy, could be used to identify who needs extra treatment to keep their cancer from coming back.

At the University of Aberdeen, another of our research teams has developed an app to help people who have already been successfully treated for melanoma check their skin and share images of any concerning changes with a specialist. The team is now refining the app to make it easier to use, especially for people who might feel anxious about checking for possible signs of cancer.

Connect world/Shutterstock.com

How can I spot skin cancer?

For most people, there’s no need to do regular skin checks. But if you notice a change or spot something unusual, speak to your doctor. In most cases it won’t be cancer, but if it is, finding it at an early stage means treatment is more likely to be successful.

Melanoma can look like a new mark or mole on your skin or nail, or it can start from a mole that has been there for a while and changed. It could also be sore, itchy, bleeding or crusty.

You can use the ‘ABCDE’ method to remember what mole changes to look out for. Tell your doctor if you notice one of them.

Asymmetry – The two halves of your mole don’t look the same
Border – It might be irregular, blurred or jagged
Colour – It may be uneven with different colours, or be different from other moles
Diameter – It might be the width of a pencil (6mm or more), and could be getting bigger or changing shape
Evolving – Anything that changes over time

Melanoma in people with brown or black skin may be more difficult to see. The mole or abnormal patch of skin might:

not show any of the ABCD signs
be symmetrical
be broken and sore (ulcerated)
be a pink colour
be under a finger or toe nail
be on the palm of the hand or sole of the foot

Melanoma and non-melanoma skin cancers can look different. Common symptoms of non-melanoma skin cancer include a sore or area of skin that:

doesn't heal within four weeks
looks unusual
hurts, is itchy, bleeds, crusts or scabs for more than four weeks

You can find out more about symptoms of melanoma skin cancer and symptoms of non-melanoma skin cancer on our information pages

A dermatoscope, a special tool doctors use to look at marks on people's skin.

Evgeniy Kalinovskiy/Shutterstock.com

Research spotlight: Improving skin cancer diagnosis

It’s not possible to diagnose a skin cancer simply by examining a mark on the skin. Doctors also need to perform a biopsy, which involves removing cells from the area and directly testing them for signs of cancer.

Unfortunately, biopsies can be uncomfortable and can cause people anxiety. Many are also done unnecessarily, when there isn’t a cancer to diagnose.

Dr Sylvain Ladame and his team at Imperial College London have an idea to make the diagnosis process work better. They're developing a non-invasive skin patch that could help doctors determine who should have a biopsy and who doesn’t need one.

The patch will work by measuring the acidity of fluid in the skin around an unusual spot. More acidic fluid could indicate cancer, so people with this symptom would be referred for biopsies.

This is early-stage work, but the team hope that one day their patch could be used to help doctors diagnose skin cancer early without causing unnecessary discomfort.

A tissue biopsy showing melanoma cells

Is skin cancer curable? How is it treated?

Yes, skin cancer can be cured.

In fact, the cure rates for non-melanoma skin cancer are very high. Doctors can almost always cure basal cell skin cancers, which very rarely spread to other parts of the body. Squamous cell skin cancers are more likely to spread, but doctors can cure most of these too.

The main treatment for these cancer types is surgery. Radiotherapy is also an option (as our researchers first showed all the way back in 1903), along with chemotherapy and immunotherapy creams.

The outlook is also positive for most people with melanoma skin cancer, especially when it’s diagnosed at earlier stages. Almost everyone diagnosed with stage 1 melanoma skin cancer in England will survive their cancer for five years or more.

The risk of dying from melanoma increases when it’s diagnosed at later stages, but, overall, 9 in 10 people with melanoma skin cancer in England will survive at least 10 years. With new treatments, some people with stage 4 melanoma are also living for a long time after their diagnosis.

Surgery is the main treatment for melanoma skin cancer. When surgery isn’t possible, or to help make sure it’s effective, doctors can also use chemotherapy, immunotherapy and targeted cancer drugs.

Doctor hand with surgical gloves checking patched surgery wound

Thunderstock/Shutterstock.com

Our impact: Targeting melanoma cells

In 2002, we found that DNA damage affecting a gene called BRAF is linked to more than 1 in 2 cases of melanoma. Then, in 2006, we showed that a new chemical could stop BRAF gene changes from driving cancer. This was an early version of the drug vemurafenib, the first new melanoma treatment in more than a decade and the first targeted treatment for the disease. 

Vemurafenib has now benefitted hundreds of people with skin cancer - improving survival by more than 50% in clinical trials.

What are researchers doing about skin cancer today?

Now, our researchers are building on the 120 years of progress we’ve already made in preventing, diagnosing and treating skin cancer. One of the most exciting ways they’re doing that is by working with our immune system to fight the disease.

At the Institute of Cancer Research in London, Professor Alan Melcher and Professor Kevin Harrington are modifying harmless viruses to chase down cancer cells. By pairing these viruses up with immunotherapy drugs, the team are hoping to create new treatment combinations that help the immune system see cancers that would otherwise be hidden.

Meanwhile, at our Cambridge Centre, Dr Pippa Corrie is leading an investigation into the complex links between the immune system and the gut microbiome, the community of bacteria that lives in our guts. To start, her team will be analysing poo samples from people with melanoma to check whether specific gut bacteria have a positive or negative effect on immunotherapy. That work could help us identify ways of manipulating the microbiome to boost the immune system's cancer-stopping capabilities.

We’re also studying exactly how skin cancers spread. Dr Amaya Viros and her team at our Manchester Institute are tracking the changes cancer cells undergo as they move through the body. They’re looking for a way to turn the most dangerous thing about cancer into a weakness we can use to keep the disease under control. One day, we could specifically target any vulnerabilities cancer cells pick up as they develop and grow.

But even that wouldn’t be the end of our work. Far from it. Because skin cancer is so often preventable, we know we can make the biggest difference by going back to the beginning and stopping it before it starts. That’s something we can contribute to this summer.

Remember, spend time in the shade, cover up with clothes and apply sunscreen regularly. We’ll keep updating you with our latest skin cancer research as it happens.

Photo by Laura Ashman

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