Lung cancer is an illness.
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body . Lung cancer , also known as lung carcinoma , is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung . The vast majority ( 85 % ) of cases of lung cancer are due to long-term tobacco smoking . This makes it the most common cause of cancer-related death in men and second most common in women after breast cancer . Overall , 17.4 % of people in the United States diagnosed with lung cancer survive five years after the diagnosis , while outcomes on average are worse in the developing world .