Lung cancer begins when abnormal cells in the lungs grow out of control¹. There are different types of lung cancer: lung carcinoid tumors are responsible for fewer than 5 percent of cases, small-cell lung cancer makes up about 10 to 15 percent of cases, and non-small cell lung cancer accounts for 80 to 85 percent of cases². Most often, when someone refers to lung cancer, they are referring to non-small cell lung cancer, which is what will be examined here.