Mediastinoscopy (say "mee-dee-yass-tuh-NAW-skuh-pee") is a procedure that looks at the space behind your breastbone and between your lungs. This area is called the mediastinum (say "mee-dee-ya-STY-num").
During the test, a doctor makes a small cut (incision) in the neck just above the breastbone. Sometimes the cut is made on the left side of the chest next to the breastbone. Then the doctor places a lighted tube into the cut. The tube lets the doctor look around inside that space.
This test is done to look for problems such as infection, inflammation, or cancer. The doctor may use the tube to take a sample of tissue from the area. This is called a biopsy. The sample can then be looked at under a microscope for problems.
This procedure usually takes about an hour.