Mediastinal lymph nodes are not diseases; they are lymph nodes within the mediastinum. In a normal person, the mediastinum includes the trachea, esophagus, heart, and aortic arch. Usually, disease is only considered when there are normal lymph nodes such as enlarged mediastinal lymph nodes. With enlarged mediastinal lymph nodes, the usual situation requires consideration of metastatic cancer or metastases, such as thyroid cancer, which can cause enlarged mediastinal lymph nodes, lung cancer, and other tumors. Systemic metastases are also usually found in enlarged lymph nodes within the mediastinum. In most cases, an enlarged lymph node within the mediastinum requires a systemic examination to identify the primary cancer. If the primary cancer cannot be found, metastatic cancer is considered and has metastasized to the mediastinal lymph nodes, resulting in enlarged lymph nodes. At this point, it indicates that the tumor or cancer may be more malignant and also indicates that the patient’s disease is in the middle to advanced stage.