Risks and Causes

Read about the causes of lung cancer, including lifestyle factors and other medical conditions. And find out what you can do to reduce your risk.

Anything that increases your risk of getting a disease is called a risk factor. Different diseases have different risk factors.

Some risk factors increase the risk of developing lung cancer. But having any of these risk factors doesn’t mean that you will definitely develop cancer.

Risks and causes

Other possible causes

Stories about potential causes of cancer are often in the media and it isn’t always clear which ideas are supported by evidence. There might be things you have heard of that we haven’t included here. This is either because there is no evidence about them or the evidence is unclear.

Grades of lung cancer

Grading is a way of dividing cancer cells into groups based on how the cells look under a microscope. This gives you and your doctors an idea of how quickly or slowly the cancer might grow and whether it is likely to spread.

There are 2 main types of lung cancer: non small cell lung cancer and small cell lung cancer. Grading is not used for small cell lung cancer.

Grades of non small cell lung cancer

Grade 1

The cells look very like normal cells. They tend to be slow growing and are less likely to spread than higher grade cancer cells. They are called low grade.

Grade 2

The cells look more abnormal and are more likely to spread. This grade is also called moderately well differentiated or moderate grade.

Grades 3 and 4

The cells look very abnormal and not like normal cells. They tend to grow quickly and are more likely to spread. They are called poorly differentiated or high grade.