Uncommon primary mediastinal tumours.

The mediastinum is a unique anatomic area containing several structures and pluripotent cells that allow for the development of a range of tumours. Uncommon neoplasms of the mediastinum account for less than 10% of all mediastinal masses and include primary thymic carcinomas, neuroendocrine carcinomas, germ-cell tumours (GCTs), lymphomas, and neurogenic, endocrine, and mesenchymal tumours. Primary thymic carcinomas and neuroendocrine carcinomas, although rare, are highly malignant lesions. GCTs are thought to derive from primitive germ cells and can be classified in seminomatous and non-seminomatous GCTs. They are located predominantly in the anterior mediastinum, as are the primary mediastinal lymphomas that include Hodgkin lymphoma, large B cell lymphoma, and lymphoblastic lymphoma. Neurogenic tumours may arise from peripheral nerves, sympathetic ganglia, or rarely parasympathetic ganglia and are located predominantly in the posterior mediastinum. Endocrine tumours are the ectopic thyroid and parathyroid tumours. Mesenchymal tumours are rare tumours and no less problematic than they are in peripheral sites. The clinical, radiological, and therapeutic aspects of these tumours are reviewed.