In some cases, a chest X-ray can spot cancer. The bigger the tumor the better the odds it is seen on X-ray. Unfortunately, X-ray will not identify all lung tumors or cancer which has spread from other locations. Not all tumors are visible.
What does a lung tumor look like on chest X-ray?
Lung tumors often look like white areas amidst the dark of the normal lung. Other diagnosis such as infection, scarring, lung collapse, or benign growths can look like cancer. We therefore often need old studies, follow up studies or further testing with CT when we see an abnormality on chest X-ray.
Lung tumors can be under a centimeter or the size of a softball. The ability to see tumors under a centimeter is limited. Even some larger tumors are not well seen because they are in areas which are hidden to the radiologist. The hidden tumors may be behind a rib, along the spine, along the mediastinum or along the diaphragm.
Can a chest X-ray diagnose cancer?
A negative chest X-ray does not mean there is no tumor present. A positive chest X-ray with an abnormality which looks like cancer may not represent cancer. The presence of old studies showing stability helps us. Tumors will grow whereas benign abnormalities will be stable or go away over time.
Further testing with CT often helps. This can show us that the white area in an X-ray is indeed a tumor. Follow up studies help as well. Pneumonia will go away with treatment on follow up whereas tumors will not.
PET CT can help with nodules. Nodules which are hot will be more suspicious for cancer then those which are not. There is overlap between tumors and infections which can both be hot. Some tumors will not be hot on a PET scan.
A chest X-ray can spot cancer. When cancer is suspected, further workup is almost always needed. This will include CT. If the abnormality is still suspicious, then a biopsy will often be needed to confirm cancer.
If no cancer is identified on a chest X-ray, then this does not mean there is no cancer. If there is concern for cancer or risk factors such as smoking, then a CT is a much better test. CT will identify most cancers in the lungs. CT will identify spread of cancer from other organs.