Voluminous masses of the mediastinum

Volumetric lesions of the mediastinum are represented by various cysts and tumors; their probable causes depend on the patient's age and the localization of the formation in the anterior, middle or posterior mediastinum.

The lesions may be asymptomatic (in adults) or cause airway obstruction (in children). Diagnosis is made using CT, biopsy of the lesion, and additional studies if necessary. Treatment of mediastinal masses is determined by the cause of the disease.

What causes mediastinal masses?

Volumetric formations of the mediastinum are divided into those located in the anterior, middle and posterior mediastinum. Each of these spaces contains characteristic volumetric formations. The anterior mediastinum is limited by the sternum (in front), the pericardium and the brachiocephalic vessels (in back). The middle mediastinum is located between the anterior and posterior mediastinum. The posterior mediastinum is limited by the pericardium and trachea (in front) and the spine (in back).

The most common mediastinal masses in children are neurogenic tumors and cysts. In adults, neurogenic tumors and thymoma are the most common masses in the anterior mediastinum; lymphomas (Hodgkin's and non-Hodgkin's) are most common in patients aged 20 to 40 years in the anterior mediastinum.

Symptoms of mediastinal masses

The symptoms of mediastinal masses depend on their location. Many are asymptomatic. Malignant tumors are much more likely to cause clinical symptoms than benign tumors. The most common symptoms of mediastinal masses are chest pain and weight loss. In children, mediastinal masses are most likely to cause compression of the trachea and bronchi and stridor or recurrent bronchitis or pneumonia. Large anterior mediastinal masses may cause dyspnea when lying supine. Middle mediastinal masses may compress blood vessels or airways, leading to superior vena cava syndrome or airway obstruction. Posterior mediastinal masses may compress or extend into the esophagus, leading to dysphagia or odynophagia.

Diagnosis of mediastinal formations

Mediastinal masses are most often discovered incidentally during chest X-rays or other imaging studies performed because of clinical symptoms in the chest. Additional diagnostic studies, usually imaging and biopsy, are performed to determine the type of mass.

Differential diagnostics of space-occupying lesions of the mediastinum

Age	Front	Average	Back
Adults	Aneurysm of the anterior semicircle of the aorta Ectopic thyroid tissue Lymphoma Hernia of the foramen of Morgagni Pericardial cyst Teratoma Thymoma	Azygos vein Bronchogenic cyst Ectopic thyroid tissue Esophageal anomalies Hiatal hernia Lymphadenopathy Varicose veins Vessel aneurysm	Aneurysm of the descending aorta Neurogenic tumors Infection of paravertebral tissues
Children	Ectopic thyroid tissue Lymphoma Sarcoma Teratoma Thymus: Cyst Histiocytosis Histoplasmosis Normal Thymoma	Bronchogenic cyst Cardiac tumor Hygroma Esophageal duplication Hemangioma Lymphadenopathy Lymphoma Pericardial cyst Vascular anomalies	Meningomyelocele Neuroenterogenic anomalies Neurogenic tumors

CT with intravenous contrast is the most informative imaging method. Chest CT can differentiate normal structures and benign tumors, particularly fatty and fluid-filled cysts, from other processes with a high degree of certainty. A reliable diagnosis can be made of many mediastinal masses by fine-needle aspiration or core needle biopsy. Fine-needle aspiration biopsy is usually sufficient for malignant processes, but if lymphoma, thymoma, or a tumor of the nervous tissue is suspected, core needle biopsy is almost always required. If tuberculosis is suspected, a tuberculin test is performed. If ectopic thyroid tissue is suspected, a thyroid-stimulating hormone test is performed.

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Treatment of mediastinal formations

Treatment of mediastinal masses depends on the type of mass. Some benign lesions, such as pericardial cysts, can simply be observed. Most malignant tumors must be removed surgically, but some, such as lymphomas, may benefit from chemotherapy. Granulomatous diseases should be treated with appropriate antimicrobial therapy.