A spot on the lungs seen in an X-ray is a nodule, which is a small, solid, oval or round tissue overgrowth with normal lung tissue surrounding it, states WebMD. It can also be a benign lung tumor, an abnormal, noncancerous tissue growth, such as a bronchial adenoma or hamartoma.
A lung nodule appears in approximately one of every 500 X-rays. If it is small and contains calcium and the patient is a nonsmoker under age 40, the nodule is more likely to be benign, notes WebMD. Nodules that are benign generally have a regular shape, even color and smooth edges. In many cases doctors use a series of X-rays to monitor the nodule for changes. Cancerous nodules grow quickly in a few months, while benign ones grow very slowly or not at all.