Lung cancer starts when abnormal cells grow out of control in the lung. They can invade nearby tissues and form tumors. Lung cancer can start anywhere in the lungs and affect any part of the respiratory system .
The cancer cells can spread, or metastasize, to the lymph nodes and other parts of the body.
Lung cancers are divided into small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC). Small cell lung cancers usually grow more quickly and are more likely to spread than non-small cell lung cancer.
Lung cancer is the leading cause of cancer deaths in the world.1
Most lung cancer is caused by smoking. But sometimes lung cancer develops in people who have never smoked.
Being exposed to secondhand smoke, arsenic, asbestos, radioactive dust, or radon can increase your chances of getting lung cancer. People who are exposed to radiation at work or elsewhere have a higher chance of getting lung cancer.
The first signs of lung cancer may include:
Because these symptoms are so general, many people don't suspect lung cancer. And by the time they see a doctor, often the cancer has already started to spread.
If the cancer spreads within and beyond the chest, other symptoms may occur.
Your symptoms and your medical history-especially if you have any history of cancer in your family-will help your doctor decide how likely it is that you have lung cancer and whether you need tests to be sure.
Lung cancer is usually first found on a chest X-ray or a CT scan. More tests are done to find out what kind of cancer cells you have and whether they have spread beyond your lung. These tests help your doctor and you find out what stage the cancer is in. The stage is a rating to measure how big the cancer is and how far it has spread.