Mediastinal Mass
A mediastinal mass is an abnormal growth or lesion in the mediastinum, the central area of the chest located between the lungs. The mediastinum contains the heart and great vessels, the trachea and main bronchi, the esophagus, lymph nodes, the thymus, and other important structures. A mass in this region can arise from any of these tissues and may be benign or malignant. The likely causes vary substantially with age, sex, and which part of the mediastinum is involved (anterior, middle, or posterior). CT and MRI are the primary imaging tests used to characterize a mediastinal mass and guide further evaluation.
What is it?
The mediastinum is the central compartment of the chest that lies between the two lungs. It contains many important structures, including the heart and large blood vessels, the trachea (windpipe) and main bronchi, the esophagus, the thymus gland, numerous lymph nodes, nerves, and surrounding connective tissue. A mediastinal mass is any abnormal growth or lesion in this area. Because so many different tissues are present, a wide variety of conditions can produce a mass here.
For evaluation, the mediastinum is typically divided into three compartments: anterior (front), middle, and posterior (back). Different conditions tend to favor different compartments. Anterior mediastinal masses are often referred to using the “Four Ts”: thymoma and other thymic lesions, teratoma and other germ cell tumors, “terrible” lymphoma, and thyroid extension into the chest (substernal goiter). Middle mediastinal masses are more often related to lymph nodes (enlarged from infection, sarcoidosis, lymphoma, or cancer), vascular abnormalities, bronchogenic cysts, or foregut duplication cysts. Posterior mediastinal masses are most often neurogenic tumors arising from nerves or nerve sheath cells (such as schwannomas, neurofibromas, and ganglioneuromas), particularly in children and younger adults.
Symptoms depend on the size, location, growth rate, and type of mass. Many mediastinal masses, especially small ones, cause no symptoms and are discovered incidentally on chest imaging done for other reasons. When symptoms occur, they may include chest discomfort or pressure, cough, shortness of breath, hoarseness (from involvement of the recurrent laryngeal nerve), difficulty swallowing, or facial and upper-extremity swelling if a mass presses on major veins (superior vena cava syndrome). Some lesions are associated with systemic symptoms such as fever, night sweats, fatigue, or unintended weight loss (more characteristic of lymphoma) or with specific syndromes (for example, myasthenia gravis with thymoma). In children, large posterior mediastinal masses may cause back or chest pain or, less commonly, neurological symptoms if they extend into the spinal canal.
CT of the chest with intravenous contrast is the primary imaging test for evaluating a mediastinal mass because it provides detailed information about size, location, density (including fat, fluid, or calcification), and relationship to nearby structures such as blood vessels, the airway, and the esophagus. MRI is helpful in selected cases, particularly when better evaluation of soft tissue, vascular involvement, or extension into the spinal canal is needed. PET/CT can assess metabolic activity and look for evidence of spread elsewhere. Most mediastinal masses ultimately require tissue sampling—through CT-guided biopsy, endoscopic ultrasound-guided biopsy, mediastinoscopy, or surgery—to establish a specific diagnosis. Laboratory tests (such as germ cell tumor markers in young men) may also play a role.
Important to Know
Evaluation and management of a mediastinal mass are highly individualized and depend on the suspected cause, the location and size of the mass, the patient’s age and overall health, and any associated symptoms. Care is typically coordinated by a multidisciplinary team that may include thoracic surgeons, pulmonologists, oncologists, radiation oncologists, hematologists, and interventional radiologists.
When a mediastinal mass is identified, the first goal is usually to determine the most likely diagnosis based on imaging features and clinical context, and then to obtain tissue confirmation when needed. Treatment is highly dependent on the underlying condition: thymomas and many germ cell tumors are often treated surgically, sometimes followed by chemotherapy or radiation; lymphomas are typically treated with chemotherapy and sometimes radiation, with surgery generally reserved for biopsy rather than removal; neurogenic tumors are often managed surgically; and benign cysts may be observed or removed depending on symptoms and size.
Because some mediastinal masses—such as lymphoma and germ cell tumors—respond best to non-surgical treatment, accurate diagnosis before surgical removal is important. Imaging findings are always interpreted alongside the patient’s history, physical examination, and laboratory results.
Red flag symptoms include severe or rapidly worsening shortness of breath, facial or upper-extremity swelling, severe chest pain, hoarseness, difficulty swallowing, coughing up blood, persistent fever or night sweats, or unintended weight loss. These warrant prompt medical evaluation.