Lung cancer is characterized by the uncontrolled growth of abnormal (precancerous) cells in lung tissues. The growth in abnormal cells can invade to local tissue or start to spread by the process of metastasis to other parts of the body, such as the opposite lung, lymph nodes, bones, liver etc. This disease can start in the windpipe (trachea), the main airway (bronchi) or the lung tissue. The normal functionality of the lung cells will be affected. Lung cancer is also known as lung carcinoma. Lung cancer is the second most common cancer and the leading cause of cancer death for men and women. Active exposure to tobacco is principal risk for lung cancer.