When reading a chest xray to evaluate lung cancer, you are looking for an area of increased whiteness in the lung fields which normally appear black. You evaluate this white mass for size, shape, and location.
Lay people generally do not read x-rays. A physician knows what a normal x-ray looks like, and then can spot abnormalities on the films. Neoplastic growths show up as dark masses. Lung cancer can also show up as shadows over the lungs.
