Types of lung cancer

Primary 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 15–20% (1 in 5) of lung cancers are small cell; the rest are non-small cell.

Small cell lung cancer

Small cell lung cancer is called this because when the cancer cells are looked at under a microscope they are very small. It’s sometimes called oat cell cancer.

Small cell lung cancer is usually caused by smoking and it’s rare for someone who has never smoked to develop this type of lung cancer. Small cell lung cancer is often fast-growing and can spread quite quickly.

Non-small cell lung cancer

There are three main types of non-small cell lung cancer. Sometimes it’s 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 that line the airways. This type of lung cancer is often caused by smoking.
• Adenocarcinoma This develops from the cells that 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 a microscope. It's sometimes known as undifferentiated carcinoma.

Mesothelioma

Mesothelioma| is a less common type of cancer that can affect the covering of the lungs. This 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.

Other types of lung cancer

There are other types of cancer that can affect the lungs, but they are much less common than small cell and non-small cell lung cancer.

A rare type of cancer called a carcinoid tumour| can sometimes develop in the lungs. Carcinoid tumours are a type of neuroendocrine cancer. The neuroendocrine system is a network of glands that produce hormones and send them into the bloodstream to affect the function of different organs in the body. Rarer types of cancer, such as soft tissue sarcomas|, can also develop in the lungs.