A nodule is usually a small, round shadow or spot seen on chest x-ray anywhere in the lungs. Nodules are due to infections, inflammation, or tumors. A nodule that is 1 centimeter in size or less is very unlikely to be cancer. Your mother will need to have more testing done to know what this could be. A chest CT scan is usually the next test that is done because it is more sensitive and shows more detail than a chest x-ray. The shape, smoothness, and density of the nodule will be seen on the CT scan. This will help in determining what this could be. If your mother has had previous chest x-rays or CT scans it would be helpful to locate them. Then her doctor could compare them with her most recent chest x-ray and CT scan. The comparison could be most helpful to your mother
A spot on the lung could be many things. They should compare to old x-rays to be sure it is not scarring from infection. Other possibilties are fungal infections, TB, some other infection, and yes cancer. If it doesn't resolve, they may want to consider a brochoscopy to evaluate and take specimens to rule these things out.