Understanding NSCLC: What It Is, who gets It, and how It Is found 

A lung cancer diagnosis raises so many questions at once. This guide answers the most important ones first — starting with what non-small cell lung cancer actually is, what causes it, and what the tests and scans your doctor orders really mean. 

Finding out you have lung cancer — or that someone you love does — is frightening. The first days after a diagnosis can feel like a flood of new words, tests, and decisions all at once. It can be hard to know where to start. 

This article focuses on the basics: what non-small cell lung cancer (NSCLC) is, why it develops, and how doctors find it and work out how far it has spread. Understanding these things is the foundation for everything that comes next — including the treatment decisions. 

All the information here is based on trusted sources, including the World Health Organization and leading cancer research journals. Every fact is referenced so you can check it yourself or share it with your care team. 

Key facts at a glance

• NSCLC makes up about 85 out of every 100 lung cancer cases worldwide.^1,2  

• In 2022, lung cancer caused more deaths around the world than any other cancer — about 1.8 million people.^2,6 

• Smoking is the biggest risk factor, but about 1 in 4 people with NSCLC have never smoked.¹ 

• A yearly low-dose CT scan can find lung cancer early in people at high risk — and earlier detection saves lives.^1,4 

• Gene tests on the cancer cells help doctors choose the treatment that is most likely to work for each person.³ 

What is NSCLC and how is it different from other lung cancers?

NSCLC is the most common type of lung cancer. When doctors say someone has lung cancer, there is a good chance — about 85% — it is this type.^1,2 Getting a lung cancer diagnosis is shocking, and knowing what kind of cancer you have is the first step to understanding what comes next. 

Doctors divide lung cancer into two main groups based on what the cells look like under a microscope. The first, and by far the most common, is non-small cell lung cancer (NSCLC). The second is small-cell lung cancer (SCLC), which is less common but typically more aggressive.² These two types are treated very differently, so telling them apart matters right from the start. 

Inside the NSCLC group, there are three main kinds. The first is called adenocarcinoma — the most common, making up about half of all NSCLC cases.¹ It starts in the cells that line the small airways deep in the lungs. The second is squamous cell carcinoma, which starts in the cells that line the larger airways in the centre of the lungs and makes up about 20 to 30% of cases. The third is called large cell carcinoma — a name used for cases that do not fit neatly into the first two groups.¹ 

Why does it matter which kind you have? Because the type of NSCLC affects which tests your doctor will run and which treatments are most likely to help. For example, adenocarcinoma — especially in people who have never smoked — is more likely to have a specific gene change that a targeted medicine can block. Squamous cell carcinoma is less likely to have those gene changes and is much more closely linked to smoking.¹ 

Knowing your type of NSCLC is not just a label — it is the starting point for finding the right treatment for you. 

Knowing what NSCLC is naturally leads to the next big question: why does it happen, and is there anything that could have prevented it? 

What causes NSCLC and can it be prevented?

Smoking tobacco is the biggest cause of lung cancer in the world.¹ People who smoke are 10 to 30 times more likely to get lung cancer than people who have never smoked — and the more you smoke and the longer you smoke, the higher the risk.¹ But lung cancer does not only happen to smokers. Many people are surprised to learn that about 1 in 4 people with NSCLC worldwide have never smoked at all — and this number is rising, especially among women and people of Asian background.¹ 

Other things that can raise the risk

Breathing in polluted air — both outdoors and inside the home — is an important risk factor.¹ Radon — a natural gas that can build up inside buildings — is thought to be one of the leading causes of lung cancer in people who do not smoke.¹ Certain substances at work, like asbestos or silica dust, also raise the risk. Having a family member who had lung cancer, certain long-term lung conditions, and some inherited gene changes are other factors that can play a role.² 

Can lung cancer be prevented?

Not smoking — or stopping smoking — is the single most powerful step a person can take. Quitting at any age lowers your risk and can improve outcomes even if cancer does appear later.^1,5 Avoiding passive (or secondhand) smoke, checking your home for radon, and limiting contact with harmful chemicals at work all help too. At a wider level, the World Health Organization (WHO) calls for strong tobacco control policies, smoke-free public spaces, and international efforts to cut air pollution as key strategies for reducing lung cancer deaths across whole populations.² 

Who should get a screening scan?

For people at higher risk — especially those aged 50 to 80 who smoke heavily or used to smoke heavily — a yearly low-dose CT scan of the chest can detect lung cancer earlier, when it is much easier to treat.^1,4 Large research studies have shown that this kind of regular scanning reduces the number of deaths from lung cancer by roughly 20%.¹ These scanning programmes are now available in a growing number of countries.  

Ask your doctor whether regular screening scans make sense for you, based on your age and smoking history. 

Once there is a concern about lung cancer, the next step is a series of tests to find out exactly what is going on — and how far the cancer has spread. 

How is NSCLC found, and what does staging mean?

NSCLC is often found at a late stage because the early warning signs — like a cough that won’t go away, feeling short of breath, losing weight without trying, or coughing up blood — can easily be mistaken for a chest infection or other common health problem.² There are no signs that point only to lung cancer, which is one of the main reasons it often goes undetected until it has grown or spread. If any of these signs last more than a few weeks, see a doctor. 

What tests will my doctor order?

The process usually starts with a CT scan — a powerful type of X-ray that gives detailed images of the inside of the body. A CT scan of the chest and belly is the first test in most cases. A PET scan, which shows where cells in the body are most active, is often used next to check whether the cancer has spread anywhere else in the body.¹ A scan of the brain is also recommended for most people, because NSCLC can sometimes spread there.¹ To confirm that it really is cancer and to find out what kind, a doctor will take a small piece of tissue (called a biopsy) from the lung or another affected area and look at it under a microscope.¹ 

Gene testing — and why it matters

Alongside the tissue sample, doctors now test the cancer cells for specific gene changes. This is sometimes called gene testing, biomarker testing, or molecular testing. These tests look for particular changes in genes known by names like EGFR, ALK, KRAS, RET, and others. The results can help determine whether a targeted medicine may work against your cancer.^1,3 The tests also check for a protein called PD-L1, which helps doctors predict whether a type of treatment called immunotherapy is likely to help.³  

These tests are now recommended for every person newly diagnosed with NSCLC, because knowing the results can completely change which treatment is chosen.^1,3 

What does “staging” mean?

Staging describes how far non-small-cell lung cancer (NSCLC) has spread at the time of diagnosis and is essential for estimating prognosis and guiding treatment decisions. Current staging uses the TNM classification:  

• T indicates the size of the primary tumor or its involvement of nearby structures, 

• N describes whether regional lymph nodes are affected,  

• and M indicates the presence or absence of distant metastases.  

By combining T, N and M categories, NSCLC is grouped into stages I to IV, ranging from very early disease to metastatic cancer, with clear implications for treatment planning and expected outcomes.¹ The stage of the cancer plays a key role in deciding on treatment.¹  

In summary

NSCLC is the most common type of lung cancer — and while a diagnosis is serious, understanding what you are dealing with is an important first step. Knowing your type of NSCLC, what caused or may have contributed to it, and what the tests and staging results mean puts you in a stronger position to have meaningful conversations with your care team. 

The good news is that tools for finding lung cancer earlier are improving, and gene testing now means treatments can be matched much more precisely to each person’s cancer than was possible even a decade ago. 

FAQ

1. What is the difference between NSCLC and small-cell lung cancer? 

Both are types of lung cancer, but they come from different kinds of cells and behave very differently. NSCLC makes up about 85 out of every 100 lung cancer cases and usually grows more slowly.^1,2 

Small-cell lung cancer is less common but more aggressive.² Because they behave differently, they are treated differently — which is why getting the right type identified from the start is so important. 

2. Can NSCLC happen to people who have never smoked? 

Yes — and it is more common than most people think. About 1 in 4 people with NSCLC worldwide have never smoked.¹ This group is mostly women, across all ages and backgrounds.¹ Risk factors for non-smokers include air pollution, radon gas in buildings, certain chemicals at work, family history of lung cancer, and some inherited gene changes.² Lung cancer in non-smokers is now thought to be among the five most common causes of cancer death worldwide and is a growing area of research.¹ 

3. What warning signs might mean someone has NSCLC? 

Common warning signs include a cough that does not go away or gets worse, coughing up blood, feeling short of breath without much effort, chest pain, losing weight without trying, feeling very tired all the time, and getting chest infections that keep coming back.² The difficult thing is that early NSCLC often causes no warning signs at all — or only very mild ones that are easy to dismiss as an ordinary cold or chest bug.² This is one of the main reasons lung cancer is often found late. If any of these signs last more than a few weeks, please see a doctor. 

4. What is gene testing and why does my doctor want to do it? 

Gene testing — sometimes called biomarker or molecular testing — looks at the DNA inside your cancer cells to find specific changes that are causing the cancer to grow.^1,3 Some of these changes can be targeted with medicines made specifically to block them, often leading to better results with fewer side effects than standard chemotherapy. The tests also check for a protein called PD-L1, which helps predict whether a type of treatment called immunotherapy is likely to help.³ These tests are now recommended for everyone newly diagnosed with NSCLC, because the results can completely change which treatment is the best fit for you. 

5. What does staging mean and why does it matter? 

Staging is how doctors describe how far the cancer has spread in the body. It runs from Stage I — where the cancer is small and only in one spot in the lung — to Stage IV, where it has spread to other parts of the body such as the liver or brain.¹ The stage is one of the most important factors doctors consider when deciding on treatment.¹

This article was written with the assistance of generative AI technology and reviewed for accuracy.