대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Bronchogenic Cyst (Mediastinal type)

Radiologic Findings

Contrast-enhanced CT scans show awell-defined, ovoid, little-enhancing, low-attenuation mass in the precarinal region.
On mediastinoscopic surgery, a well-defined cystic mass was found.

Brief Review

Bronchogenic cysts are congenital lesions resulting from abnormalities in ventral budding or branching of the bronchopulmonary foregut.
The lesions have been classified as mediastinal and intrapulmonary types.
Mediastinal cysts are far more frequent and do not communicate with the bronchial tree, unlike intraparenchymal cysts in which such communications usually develop, leading to frequent recurrent infection.

Most bronchogenic cysts are most commonly located in the carinal area (52%), followed by paratracheal area (19%), esophageal wall (14%), and retrocardiac area (9%).
These cysts rarely can be seen in other locations such as the anterior mediastinum, the low posterior mediastinum, or in the lung itself.

Their classic chest radiographic findings are clearly defined round or oval masses of water density, commonly located just inferior to the carina.
These thin-walled cysts are lined with respiratory epithelium and cyst fluid is composed primarily of water admixed with varying amounts of thick proteinaceous mucus. Calcium oxalate crystals have also been detected in the fluid.
This variable fluid composition explains the different CT attenuations observed in bronchogenic cysts.

Usually, CT of bronchogenic cyst shows a mass with the same attenuation as that of water, reflecting their serous nature.
However, in one-half of all bronchogenic cysts, the CT density can vary from a low soft-tissue range to higher-than-muscle density, likely due to intracystic hemorrhage, protein, or calcium.


Those patients who are asymptomatic and have small cysts with typical CT findings can be followed. If a malignant neoplasm is suspected because CT findings are atypical or the mass has increased in size, surgery or aspiration may be required for diagnosis and treatment.

References

1. Nakata H, Nakayama C, Kimoto T, et al. Computed tomography of mediastinal bronchogenic cysts. J Comput Assist Tomogr 1982;6:733-738
2. Naidich DP, Zerhouni EA, Siegelman SS. Computed tomography and magnetic resonance of the thorax. 2nd ed. Philadelphia: Raven Press, 1991:120-123
3. Glazer JS, Siegel MJ, Sagel SS. Low-attenuation mediastinal masses on CT. AJR 1989;152:1173-1177
4. Mendelson DS, Rose JS, Efremidis SC, Kirschner PA, Cohen BA. Bronchogenic cysts with high CT numbers. AJR 1983;140:463-465

Keywords

Mediastinum, Congenital,