Benign lesions (another word for abnormal spots or coin nodules) are usually due to old infections that have healed to form a scar. Malignant lesions are usually due to lung cancer or cancer that has spread from elsewhere in the body to the lungs. Utilizing only the routine chest x�ray it is seldom possible to differentiate between benign and malignant lesions. This difference is critical since a malignancy (cancer) may be in its early stages and amenable to surgery. Conversely, a benign lesion usually warrants no treatment and will not affect the patient's life. What to do after finding a coin nodule on chest x�ray depends on the patient's age, smoking history, availability of old x�rays, and a host of other factors.
A lung infiltrate is an abnormality on chest x�ray larger than a coin lesion or spot. It is also non�specific and may be due to a variety of causes: pneumonia, partial lung collapse, cancer, tuberculosis, and pulmonary blood clots are common examples.