Lung cancer
Lung cancer is when abnormal cells in the lung start to divide and grow in an uncontrolled way. It starts in the windpipe (trachea), the main airway (bronchus) or the lung . Cancer that starts in the lung is called primary lung cancer.
There are 2 main types of primary lung cancer:
non small cell lung cancer
small cell lung cancer
The most common type is non small cell lung cancer.
Primary lung cancer is different to cancer that spreads to your lungs from somewhere else in your body. This is called secondary lung cancer or lung metastases.
Read more about secondary lung cancer
The lungs are part of the breathing system, which is also called the respiratory system. The breathing system includes:
the nose and mouth
windpipe (trachea)
airways to each lung (left and right bronchus)
lungs
The right lung is divided into 3 sections called the upper, middle and lower lobes. The left lung is divided into 2 sections called the upper and lower lobes.
Your lungs have a system of tubes that carry oxygen in and out as you breathe.
The windpipe divides into two tubes, the right bronchus and left bronchus. These split into smaller tubes called secondary bronchi. They split again to make smaller tubes called bronchioles. The bronchioles have small air sacs at the end called alveoli.
In the air sacs, oxygen passes into your from the air breathed in. Your bloodstream carries oxygen to all the cells in your body. At the same time carbon dioxide passes from your bloodstream into the air sacs. This waste gas is removed from the body as you breathe out.
The pleura or pleural membranes are 2 fibrous sheets of tissue. They cover the lungs and help to protect them.
The gap between the pleura is called the pleural space. The pleura make a lubricating fluid. The fluid keeps the pleura moist, so they slide easily over each other as we breathe in and out.
Lung cancer cells can spread to the pleura. The cancer cells inflame the pleura and they then make too much fluid. The fluid collects in the pleural space and stops the lung from expanding fully. This can make you feel breathless. Build up of fluid between the pleura is called a pleural effusion.
Read about a pleural effusion and how it is treated
Lymph nodes (also called lymph glands) are close to the lungs and airways. They are part of the lymphatic system. This is a network of tubes and glands in the body that filters body fluid and fights infection and illnesses like cancer.
Lymph fluid circulates through body tissues. Cancer cells may be released from a lung tumour and trapped in nearby lymph nodes.
When you are diagnosed, your surgeon or cancer specialist (medical oncologist) checks your lymph nodes for cancer cells.
Lung cancer can start in any part of the lungs or airways.
Lung cancer is the third most common cancer in the UK. Around 49,300 people are diagnosed in the UK each year.
Lung cancer is more common as you get older. 45 out of 100 people (45%) diagnosed with lung cancer in the UK are aged 75 and older.
In the UK each year:
around 25,500 men are diagnosed
around 23,900 women are diagnosed
More than 60 out of 100 lung cancer cases in the UK (more than 60%) are caused by smoking.
Other causes or risk factors include:
exposure to radon gas
exposure to certain chemicals in the workplace
a family history of lung cancer
certain cancer treatments for other types of cancer
A rare cancer called mesothelioma starts in the protective sheets that cover the lungs (pleura). This is very different to lung cancer.
Cancer can spread into the lung from other parts of the body. This is called secondary lung cancer or lung metastases.
Last reviewed: 07 Oct 2025
Next review due: 06 Oct 2028
Lung cancer doesn't always cause symptoms in its early stages. Symptoms can include a cough that won't go away, coughing up blood and breathlessness.
You usually start by seeing your GP, and they might refer you to a specialist and organise tests. Or you might be referred to a specialist and further tests if screening for lung cancer or a lung health check showed that you might have lung cancer.
Metastatic lung cancer means that the cancer has spread from where it started in the lung to other parts of the body. It is also called advanced lung cancer.
The stage of a cancer tells you how big it is and whether it has spread. Doctors use the TNM or number staging systems to stage lung cancer. They might also use limited and extensive stages to stage small cell lung cancer.
There are 2 main groups of primary lung cancer, namely small cell lung cancer (SCLC) and non small cell lung cancer (NSCLC). The most common type is non small cell lung cancer.
Lung cancer starts in the windpipe (trachea), the main airway (bronchus) or the lung tissue. Cancer that starts in the lung is called primary lung cancer.
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