A nodule is usually a small, round shadow seen on chest x-ray anywhere in the lungs. Nodules are due to infections, inflammation, or tumors. You will need to have more testing done to know what this could be. A CT scan of your lungs is the most appropriate next step. If you have had previous chest x-rays or CT scans it would be helpful to locate them. Then your doctor could compare them with your most recent chest x-ray and CT scan. The comparison could be most helpful to your doctors, in interpreting these findings and the significance of the nodule.
15 millimeters (mm) equals 2/3 of an inch.