Chest (Mediastinal) Cysts

Mediastinal cysts and tumors are relatively common in infants and children. Although cysts of the mediastinum are often asymptomatic, they usually require removal. If cysts are symptomatic, they may present with chest pain, cough, breathing problems, bloody cough or bloody vomiting, and difficulty swallowing. The various cysts encountered include bronchogenic cysts, thymic cysts, enterogenous cysts, neurenteric cysts, dermoid cysts, cystic hygroma, and pericardial cysts.

Diagnostic studies include chest x-rays, CT scan or MRI, dye (contrast) study of the esophagus, and occasionally ultrasound. Esophagoscopy (looking into the esophagus), bronchoscopy (looking into the airways of the lung), and arteriography (injecting dye into the arteries and taking s-rays) may be useful in selected cases. The exact preoperative diagnosis is often not possible without either a biopsy or examination after removal.

Thymic Cysts
Thymic cysts arise from the thymus gland and occur in the front of the chest. They usually do not cause symptoms. They may have the potential to undergo cancerous changes. Thymic cysts may present with symptoms including wheezing and lung infections. They can expand rapidly as a result of either bleeding within the cyst or infection. In general, when recognized, thymic cysts should be removed because of these potential complications.

Esophageal Duplication Cysts
Esophageal duplication cysts share a common wall with the normal esophagus (Figures 1 and 2). These cysts communicate with the inside of the esophagus in 20% of cases. Neck or chest vertebral abnormalities often are associated with esophageal duplication cysts. Very rarely, these cysts may attach to or communicate with the spinal canal or occasionally to the dura (lining of the spinal cord) and are then referred to as neurenteric cysts. Patients with neurenteric cysts may present with pain or neurologic findings. They are at risk for developing complications such as paraplegia (paralysis of the lower body) and meningitis. In addition, it is common (10% to 15%) for an esophageal duplication cyst to be accompanied by an intestinal duplication in the abdomen.

Esophageal duplication cysts may also extend down through the diaphragm to end blindly in the abdomen or may communicate with the small intestine (Figure 2).

Figure 3.  Diagram of duplication of the esophagus communicating with the jejunum (beginning of the small intestine).

Rarely, multiple esophageal duplication cysts have been observed. The presence of abnormal stomach tissue within the cyst can result in ulcers, bleeding, or rupture of the cyst or nearby intestinal tissue. Duplication cysts may enlarge suddenly and push on the lungs or normal esophagus causing breathing problems or difficulty swallowing. For these reasons, removal of the cyst is recommended when they are found. Patients with neurenteric cysts may require the expertise of a pediatric surgeon and neurosurgeon for removal.

Cystic Hygromas
Cystic hygromas are thin-walled, cysts containing lymphatic fluid. Most patients are born with these cysts. They most commonly arise in the neck. In 10% to 15% of cases, the cyst extends into the chest from the neck (Figure 4). Rarely, they may arise primarily within the chest. Bleeding into the cyst or infection may cause the cysts to enlarge rapidly and result in pressure on the airway and sudden onset of problems with breathing. This may require an urgent operation.

Pericardial Cysts
The pericardium is the sac surrounding the heart. Pericardial cysts most often appear on a routine chest x-ray and do not cause problems. They are usually on the right side of the heart. These cysts are thin walled, contain clear fluid, and may be removed easily to make sure that they are not cancerous.

Dermoid Cysts
Dermoid cysts are some of the largest chest tumors seen in children. The typical dermoid cyst is thick-walled, containing various parts of skin, hair, occasionally teeth, and caseous (cheesy) material. The tumors are usually found in the front of the chest, but rarely are located within the pericardium (the sac that surrounds the heart). Dermoid cysts rarely become cancerous. Removal of dermoid cysts is warranted because of the risk of infection and potential rupture. When that happens, the patient occasionally may present by coughing up hair.

Bronchogenic Cysts
Bronchogenic cysts are located in the middle of the chest. These cysts originate before the airways of the lungs are formed in the fetus and persist after birth. They are usually located close to the first branching of the windpipe (trachea) known as carina (Figure 5).

Bronchogenic cysts form when epithelial cells from the developing trachea and lung are pinched off and become separated from the airways. Bronchogenic cysts are usually, but not always, outside of the lung (Figure 6). They do not communicate with the normal airways. In addition, bronchogenic cysts do not contain air sacs (alveoli).

Under the microscope, bronchogenic cysts are thin walled and often contain cartilage and sometimes glands from the airways. These cysts often have no symptoms and may be noted as an unexpected finding on a chest x-ray. Bronchogenic cysts in the area of the carina can compress the trachea, however, resulting in breathing problems in newborns.

They may be detected on chest x-ray or CT scan of the chest. Symptomatic cysts should be removed. Asymptomatic cysts should also be removed because of the risk of infection. A rare case of cancer in a bronchogenic cyst occurring in an 8-year-old girl has been reported. Most bronchogenic cysts can be removed safely using thoracoscopic techniques. Thoracoscopy may be contraindicated in children with cysts under the carina. In some cases, it is extremely difficult to separate the wall of the cyst from the normal airway. Near-complete removal and leaving the attached portion of the cyst wall on the airway is reasonable treatment and has not been associated with recurrence.

Article and graphics adapted from O'Neill: Principles of Pediatric Surgery. © 2003, Elsevier.

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