The lungs are the primary organ in respiration. They are sponge-like organs that are divided into lobes. Although the right lung has three lobes, the left lung has only two lobes due to the position of the heart, which is toward the left side of the body.
During respiration, air travels through the nose, down the trachea or windpipe, and into the bronchus. The bronchus branches into narrower bronchioles and then into smaller and smaller airways ending in air sacs called alveoli. It is at the alveoli that oxygen is exchanged for carbon dioxide.
Most cancerous changes occur in the lungs long before any symptoms are present. There are many types of lung cancer, but the most common lung cancer is bronchogenic carcinoma, which begins as a tumor in the lining of the bronchi. Lung cancer can also be present in the trachea, the bronchioles, or the alveoli.
Lung cancer is the leading cause of cancer deaths among men and women, but the most alarming news is that more women will die from lung cancer than will die from breast cancer. Cigarette smoking poses the greatest risk for developing lung cancer.