Lung cancer
Lung cancer is the malignant transformation and expansion of lung tissue, and is the most lethal of all cancers worldwide, responsible for 1.3 million deaths annually. It is caused mainly by cigarette smoking, and mostly affects men, being the leading cause of death of men between the ages of 40 and 65. With increased smoking among women, lung cancer is now occurring more frequently in women. While some people who have never smoked do still get lung cancer, this appears to be due to a combination of genetic factors and exposure to secondhand smoke. Air pollution may also contribute to the development of lung cancer.