A primary or metastatic malignant neoplasm affecting the mediastinum. Representative examples of primary malignant mediastinal neoplasms include malignant germ cell tumors, malignant mesenchymal tumors, lymphomas, and malignant peripheral nerve sheath tumors. A representative example of metastatic malignant neoplasm to the mediastinum is the metastatic carcinoma to the mediastinum from another anatomic site. [from
NCI]