Mediastinoscopy. A mediastinoscope is inserted into the chest through an incision above the breastbone to look for abnormal areas between the lungs. A mediastinoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a cutting tool. Tissue samples may be taken from lymph nodes on the right side of the chest and checked under a microscope for signs of cancer. In an anterior mediastinotomy (Chamberlain procedure), the incision is made beside the breastbone to remove tissue samples from the lymph nodes on the left side of the chest.