Small subcarinal or hilar bronchogenic cysts, and small thymic cysts were found as homogenous water density masses on chest CT. Barium swallow studies and/or esophagoscopy were performed mainly for patients for suspected esophageal and bronchogenic cysts. CT was performed in patients after 1980, which revealed round, well-circumscribed masses of water density or a little higher. In the early series when CT was not available, induced pneumomediastinum was a diagnostic tool used to demonstrate the size, shape, and extent of the mediastinal masses. MRI was recently performed in 29 patients. Compared to the low signal intensity in T1-weighted images, the bright signal intensity in T2-weighted images indicated the cystic content of the mediastinal mass, which was a characteristic sign that differentiated a solid mediastinal mass. In this sense, MRI has provided specific diagnostic confirmation in regard to mediastinal cysts (Fig 1, 2). More info
For example, in 1970, we performed an axillary thoracotomy with a preoperative diagnosis of neurogenic tumor in the posterior mediastinum for a patient with von Recklinghausen disease, which was found to be a meningocele at surgery. In 1997, we encountered another patient with a meningocele whose MRI showed the anatomy of that cyst clearly (Fig 3), and thus a definite preoperative diagnosis was obtained. However, we failed to diagnose small thymic cysts because of a lack of their characteristic signs in MRI. For one particular patient with thoracic duct cyst, a lymphangiogram was performed to obtain a definite preoperative diagnosis. With recent advancements in radiologic techniques, needle aspiration was rarely performed after establishing the clinical diagnosis.
The clinical characteristics of mediastinal cysts are shown in Table 3.
Figure 1. Chest CT scan (top) and MRI (bottom) of the subcarinal bronchogenic cyst.
Figure 2. Chest CT (top) reveals an anterior mediastinal mass. It was found to be a cystic mass by T2-weighted images in MRI (middle). A resected specimen reveals a thymic cyst containing serous fluid (bottom).
Figure 3. Chest radiograph on hospital admission shows a round, well-circumscribed shadow 10 cm in diameter in the in the lower right chest (top left). A right lateral view shows a mass in the posterior mediastinum (top right). MRI (bottom) clearly demonstrated paravertebral cysts communicating with the vertebral canal.
Table 3—Clinical Characteristics in Cysts in the Mediastinum (Symptoms and Signs)
|Characteristics||Bronchogenic, n = 47||Esophageal, n = 4||Thymic, n = 30||Pericardial, n = 12||Pleural, n = 7||Others, n = 5||Total, n = 105|
|Chest pain||6||0||6||2||0||1t||15 (14.3)|