Mediastinoscopy (say "mee-dee-yass-tuh-NAW-skuh-pee") is a procedure that looks at the space behind your breastbone between your lungs. This area is called the mediastinum (say "mee-dee-ya-STY-num").

A small cut (incision) is made in the neck just above the breastbone or on the left side of the chest next to the breastbone. Then a thin scope (mediastinoscope) is inserted through the opening. A tissue sample (biopsy) can be collected through the scope. The sample can then examined under a microscope for problems. These may include infection, inflammation, or cancer.