If your healthcare provider thinks you have a problem in the middle of your chest, an X-ray is usually the first test done. It can often show tumors in the thymus, nearby organs, or lymph nodes.  

For this test, you lie on a table as it slides through a ring-shaped CT scanner. The scanner takes many X-rays. Then a computer combines these images to make pictures of your insides. CT scans show much more detail and can show smaller changes than chest X-rays.

MRIs use radio waves and magnets instead of X-rays to create very detailed images of the inside of your body. You may have this test if you can't have a CT scan for some reason. MRI is also very good for looking for cancer spread to the brain or spinal cord.

For this test, you’re injected with a slightly radioactive sugar. Cancer cells collect more of the sugar than normal cells. After about an hour, a special camera is used to take a picture of your whole body. It show where the radioactive sugar has collected. These spots might be cancer.

The images from PET scans are not as detailed as those from CT scans. Some machines can do a PET scan and CT scan at the same time. This test is useful if your provider thinks the cancer may have spread but isn't sure where.

For this test, a thin, hollow needle is put through your skin and into the tumor to get a sample of it. This is often done during a CT scan of your chest. This allows your healthcare provider to watch the needle go into the tumor and be sure the sample comes from the right place. Sometimes a needle biopsy doesn't get enough tissue to make a clear diagnosis.

Surgery can be done to do a biopsy. A 2-inch cut is made next to the breast bone (sternum) so a piece of the tumor can be removed. This is more involved than a needle biopsy. But it’s also more likely to provide a large enough sample for diagnosis. You may hear this called the Chamberlain procedure.