Each year, over 37,000 people in the UK are diagnosed with lung cancer. There are two main types of primary lung cancer, which behave and respond to treatment quite differently. They are:

• small cell lung cancer (SCLC)
• non-small cell lung cancer (NSCLC).

About 1 in 5 lung cancers are small cell, the rest are non-small cell.

Non-small cell lung cancer

There are three main types of non-small cell lung cancer. Sometimes it is not possible to tell which type someone has. This is because when the cells are looked at under a microscope they are not developed enough. The three types are:

Squamous cell carcinoma This is the most common type of lung cancer. It develops in the cells which line the airways. This type of lung cancer is often caused by smoking.

Adenocarcinoma This develops from the cells which produce mucus (phlegm) in the lining of the airways. This type of cancer is becoming more common

Large cell carcinoma This gets its name from the large, rounded cells that are seen when they are examined under the microscope. It is sometimes known as undifferentiated carcinoma.

A less common type of cancer that can affect the covering of the lungs is called mesothelioma. It is a cancer of the membrane which covers the surface of the lungs and lines the inside of the chest. It often occurs in people who have been exposed to asbestos.

Mesothelioma is discussed in its own section.