A cancer that begins in the lungs and most often occurs in people who smoke.

Lung cancer begins as a growth of cells in the lungs. Risk factors include smoking, secondhand smoke, exposure to certain toxins and family history.

Symptoms include cough, chest pain, wheezing and coughing up blood. Lung cancer typically doesn't cause symptoms early on. They tend to happen when the cancer is advanced.

Treatment may include surgery, chemotherapy, radiation, targeted therapy and immunotherapy.