Interior of the cecum and lower end of ascending colon with the ileocecal valve labeled as colic valve. Endoscopic image of cecum with arrow pointing to ileocecal valve in foreground.
Lung cancer is a malignant tumour that starts in the cells of the lung. Malignant means that it can spread, or metastasize, to other parts of the body. When cancer starts in lung cells, it is called primary lung cancer. The lung is part of the respiratory system. You use your lungs when you breathe.
Find out about the different types of lung cancer. The type of lung cancer you have tells you the type of cell that the cancer started in. Knowing this helps your doctor decide which treatment you need. Cancer that starts in the lung is called primary lung cancer. If cancer spreads to your lungs from somewhere else in your body, this is secondary lung cancer.