IS Case 433: Paramediastinal bronchogenic cyst
Imaging Sciences URMC 2010
Publication Date: 2010-08-27
PA and lateral views of chest demonstrated a well-circumscribed mass adjacent to the left hilum. On axial CT with and without contrast there was a dense, homogeneous, well-circumscribed mass adjacent to the left side of the heart. There were no calcifications or internal septations, and the mass did not enhance. There was no lymphadenopathy.
Paramediastinal bronchogenic cyst
Bronchogenic cysts are benign epithelial lesions, arising with the lungs during the third trimester of embryonic development as a type of foregut duplication cyst. Bronchogenic cysts are thought to represent aberrant outpouching of a supernumerary bud as the lungs emanate from the foregut. Histologically the cysts are closed sacs lined with respiratory epithelium, but may contain cartilage and mucous glands.
Historically, bronchogenic cysts have been considered asymptomatic lesions discovered incidentally on chest radiographs ordered for other reasons. However recent studies have shown the complications such as superior vena cava syndrome, airway compression, pneumothorax and pneumonia occur in up to 20% of patients.
The location of bronchogenic cysts depends on when during the stage of development the abnormal outpouching occurs, but are found in the mediastinum up to 90% of the time. When the lesion is outside the mediastinum it often occurs along the tracheobronchial tree.
Radiographically, cysts have rounded, well-defined edges. On CT the lesion appears isointense to water, but may be higher attenuation if there is internal proteinaceous materials or blood. MRI may also be used for further characterization, demonstrating homogeneous intermediate T1 and high T2 signal characteristics.
Surgical removal of bronchogenic cysts is the definitive treatment although historically asymptomatic lesions were often observed. However, given the severity of delayed complications, asymptomatic cysts should be considered for removal.
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