Cancer is uncontrolled growth of abnormal cells. Growth of abnormal cells in one or both lungs could be indicative of lung cancer. These abnormal cells have a tendency to grow but do not develop into healthy tissue of lungs. Research has shown that 87% of lung cancer is related to smoking. Risks are considerably reduced if the person quits smoking. Extent to which cancer has spread is categorized as different stages. The stage depends upon the size of tumor and areas it has spread to. Doctors decide mode of treatment based on the stage of cancer. Localized cancer in a particular part of lung is termed as Stage 1. If it has spread to the lymph nodes at the top of the lungs, it is termed as Stage 2. Cancer spreads to the chest walls during Stage 3. There is a possibility of cancer having spread to other parts of the body such as windpipe or heart, once it reaches Stage 3. Sometimes there can be fluid collection around the lungs that contain cancer cells. Symptoms of lung cancer can vary