Cysts of one of the parts of the mediastinum: the superior part, containing the trachea, esophagus, thoracic duct and thymus organs; the inferior middle part, containing the pericardium; the inferior anterior part containing some lymph nodes; and the inferior posterior part, containing the thoracic duct and esophagus.

Neoplasms composed of tissue of the mesothelium, the layer of flat cells, derived from the mesoderm, which lines the body cavity of the embryo. In the adult it forms the simple squamous epithelium which covers all true serous membranes (peritoneum, pericardium, pleura). The concept does not refer to neoplasms located in these organs. (From Dorland, 27th ed)

The testing of the acuity of the sense of hearing to determine the thresholds of the lowest intensity levels at which an individual can hear a set of tones. The frequencies between 125 and 8000 Hz are used to test air conduction thresholds and the frequencies between 250 and 4000 Hz are used to test bone conduction thresholds.