The lungs are a pair of organs in the chest that help the body inhale the oxygen it needs and exhale carbon dioxide. Lung cancer forms when cells in the lungs begin to grow rapidly and uncontrollably. These cells can invade and destroy healthy lung tissue and eventually interfere with normal respiratory function. Lung cancer cells can also invade the lymph nodes or bloodstream and metastasize (spread) to other parts of your body, where they can grow and form new tumors. There are two main types of lung cancer (non-small cell and small cell), classified by the type of cells in the tumor.