Cancer occurs when normal body cells get out of control, multiply and spread. These cells clump together to form a cancerous or malignant tumour which can then grow and damage healthy parts of the body.

Lung cancer is a malignant tumour that grows in the lung or the tissues around it. It can affect the body cells lining:

• the windpipe (trachea)
  
   
• the bronchi (the main tubes that branch off from the windpipe)
  
   
• the many small tubes that carry oxygen through the lungs.

There are two main types of lung cancer:

• small cell: one in five lung cancer patients have this type
  
   
• non-small cell: most other patients have one of three types of non-small cell cancer. Doctors tend to group them together because they are quite similar to each other.

Small cell and non-small cell cancers grow in different ways, and so need different treatments.

Lung cancer that starts in the lung is called primary lung cancer. This part of the website is about primary lung cancer.

Cancers that start elsewhere in the body may eventually spread to the lung. These are called secondary cancers and are not covered here.

There is another type of cancer that can affect the lining around the lungs. It is called mesothelioma, and is normally caused by asbestos. We hope to have information on mesothelioma on this site in the future, but it isn't ready yet.