Mediastinal Cyst
A mediastinal cyst is a fluid-filled lesion located in the mediastinum, the central area of the chest between the lungs. Mediastinal cysts include several specific types—such as bronchogenic, esophageal duplication, pericardial, and thymic cysts—and are most often congenital and benign. Many are discovered incidentally on chest imaging done for other reasons. CT and MRI are the primary imaging tools used to identify and characterize these lesions, while management depends on size, location, symptoms, and the specific type of cyst.
What is it?
The mediastinum is the central compartment of the chest located between the lungs. It contains the heart and great vessels, the trachea and main bronchi, the esophagus, the thymus, lymph nodes, nerves, and surrounding connective tissue. A mediastinal cyst is a fluid-filled lesion that develops in this area, usually from a developmental abnormality or remnant of structures that formed during early fetal development. Most mediastinal cysts are benign.
Several types of mediastinal cysts are recognized, each with its own typical location and characteristics. Bronchogenic cysts arise from abnormal budding of the early airway and are most commonly found in the middle mediastinum near the trachea or main bronchi; they contain fluid that ranges from clear to thick and may be lined by airway-like cells. Esophageal duplication cysts (a type of foregut duplication cyst) develop along the esophagus and contain fluid with a lining similar to that of the gastrointestinal tract. Pericardial cysts are thin-walled cysts arising from the sac around the heart, most often located at the right cardiophrenic angle. Thymic cysts develop in the thymus gland in the anterior mediastinum and may be congenital or acquired. Less common cysts include neurenteric cysts (associated with vertebral anomalies and located in the posterior mediastinum), lymphangiomas, and others.
Most mediastinal cysts cause no symptoms and are discovered incidentally on chest X-ray, CT, or MRI performed for other reasons. When symptoms occur, they generally relate to the size and location of the cyst and to whether it is pressing on adjacent structures. Common symptoms include chest discomfort, cough, shortness of breath, difficulty swallowing, hoarseness, or, less commonly, recurrent respiratory infections. Complications—although uncommon—can include infection within the cyst, rupture, bleeding, or rapid enlargement, any of which may produce more pronounced symptoms.
CT of the chest with intravenous contrast is the primary imaging test for evaluating a mediastinal cyst because it provides detailed information about size, location, density (including fluid, soft tissue, fat, or calcification), and relationship to nearby structures. Many cysts have characteristic features that allow them to be confidently identified on imaging, although some appear denser or more complex on CT than typical simple fluid—particularly bronchogenic cysts containing proteinaceous or hemorrhagic material—which can make accurate identification more challenging. MRI is particularly useful in these cases because it provides excellent soft-tissue contrast and can confirm the fluid nature of the lesion. Echocardiography is helpful for pericardial cysts. In selected cases, endobronchial or endoscopic ultrasound—or, less commonly, biopsy or surgical resection—may be needed to confirm the diagnosis when imaging is inconclusive.
Important to Know
Management of mediastinal cysts is individualized and depends on the type, size, and location of the cyst, the presence of symptoms, and whether complications have occurred. Many small, classically appearing cysts can be managed with periodic imaging surveillance to confirm stability, particularly when they are asymptomatic and the diagnosis is confidently established.
Surgical removal—often through minimally invasive techniques such as video-assisted thoracoscopic surgery (VATS) or robotic surgery—is typically considered for cysts that are causing symptoms, large or growing, complicated by infection or bleeding, or when the diagnosis remains uncertain after imaging. Complete removal generally cures the cyst and prevents future complications. In selected cases, image-guided aspiration of cyst fluid may be considered, though surgical removal is preferred when possible to reduce the risk of recurrence and to confirm the diagnosis.
Care is typically coordinated by primary care clinicians, thoracic surgeons, pulmonologists, and, when relevant, cardiologists. Imaging findings are interpreted alongside the patient’s symptoms, exposures, and broader clinical context.
Because most mediastinal cysts are benign and slow-growing, the goal of evaluation is to confirm the diagnosis, exclude more serious conditions that can appear similar (such as solid mediastinal tumors), and decide whether intervention is needed. Even when treatment is not pursued, documentation of the imaging features and prior measurements is important for future follow-up.
Red flag symptoms include rapidly worsening shortness of breath, severe chest pain, fever and chills with worsening symptoms, sudden hoarseness, difficulty swallowing, signs of airway compromise, facial or upper-extremity swelling, or coughing up blood. These warrant prompt or urgent medical evaluation, as they may indicate complications of the cyst or another serious condition.