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.
Primary lung cancer starts in the lungs. The cancer cells are abnormal lung cells. Sometimes, people will have cancer travel from another part of their body or metastasize to their lungs. This is called secondary lung cancer because the lungs are a secondary site compared to the original primary location of the cancer.