A mediastinoscopy is a surgical procedure performed to examine the mediastinum. The mediastinum is the space behind the sternum (breastbone) in the middle of the chest that separates the two lungs. It contains lymph nodes, the heart and its great vessels, the trachea, the esophagus, and the thymus gland.
The mediastinum can be visualized by the use of an endoscopic instrument called a mediastinoscope. A mediastinoscope is a lighted, long, thin, flexible tube that can visualize the organs and structures of the mediastinum and can transmit images onto a TV-like monitor.
The procedure is performed in an operating room under general anesthesia. The surgeon makes a small incision in the neck above the top of the sternum and inserts the mediastinoscope. In addition to directly visualizing the mediastinum, tissue samples of mediastinal lymph nodes may be obtained. These lymph nodes receive lymphatic drainage from the lungs. A biopsy of these lymph nodes helps to identify disease processes that may be present in the mediastinum and the lungs.
The primary reason for mediastinoscopy is to visualize, examine, and biopsy lymph nodes for identification of disease processes in the mediastinum, particularly the staging of lung cancer. Determining the “stage” or the extent to which cancer has spread is important in planning the proper treatment. While positron emission tomography (PET scan) is becoming more useful in staging cancer, mediastinoscopy remains an important diagnostic tool when tissue biopsy (the removal of a small tissue sample for examination) is required.