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The mediastinum is the cavity that separates the lungs from the rest of the chest. It contains the heart, esophagus, trachea, thymus, and aorta. The mediastinum has three main parts: the anterior mediastinum (front), the middle mediastinum, and the posterior mediastinum (back). The most common mediastinal masses are neurogenic tumors (20% of mediastinal tumors), usually found in the posterior mediastinum, followed by thymoma (15-20%) located in the anterior mediastinum.〔(【引用サイトリンク】title=Neurogenic Tumors of the Mediastinum )〕 Masses in the anterior portion of the mediastinum can include thymoma, lymphoma, pheochromocytoma, germ cell tumors including teratoma, thyroid tissue, and parathyroid lesions. Masses in this area are more likely to be malignant than those in other compartments. Masses in the posterior portion of the mediastinum tend to be neurogenic in origin, and in adults tend to be of neural sheath origin including neurilemomas and neurofibromas.〔 Lung cancer typically spreads to the lymph nodes in the mediastinum. ==Diagnosis== In several editions of Physical Diagnosis, concerning mediastinal tumors the author writes: :''According to Christian1 the mediastinal neoplasms which are neither so rare nor so obscure as to make diagnosis practically impossible are: (1) Sarcoma (including lymphosarcoma, leucaemic growths, and Hodgkins' disease; (2) Teratoma and cyst.'' Many signs and symptoms of a mediastinal tumor do not distinguish between these two principal classes of mediastinal tumor. However, on a radiograph usually the former class will have an irregular shape and the latter class will have a smooth spherical or ovoid shape. A large minority of patients with a mediastinal teratoma (including dermoid cyst) will cough up hair.〔 For a differential diagnosis, the key is to exclude aneurism. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「mediastinal tumor」の詳細全文を読む スポンサード リンク
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