Lung cancer is deadly, and every year, it is the leading cause of cancer death in men and women. It is a cancer that forms in lung tissues, usually in the cells that line the air passages. The types of lung cancer most often seen are small-cell lung cancer (most aggressive) and non-small cell lung cancer, which includes adenocarcinoma, squamous cell carcinoma and large-cell carcinoma, as well as other less common sub-types.