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.
As more cancer cells develop, they can form into a tumor and spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer? Types of lung cancer. The 2 main types of lung cancer are: Small cell lung cancer (SCLC), which is sometimes called oat cell cancer. About 10% to 15% of lung cancers are SCLC. Non-small cell lung cancer (NSCLC), which makes up about 80% to 85% of lung cancers. The 3 main types of NSCLC are adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. Small cell and non-small cell lung cancers are treated differently. The information here focuses on small cell lung cancer. See Lung Cancer (Non-Small Cell) for information about that type of lung cancer. Other types of lung cancer and tumors. Lung carcinoid tumors: Less than 5% of lung tumors are carcinoid tumors of the lung. Most of these grow slowly. For more information about these tumors, see Lung Carcinoid Tumor.