[Imaging of bronchogenic cysts]

Bronchogenic cysts, unlike the other mediastinal cysts, exhibit a high incidence of complications, which makes their resection advisable even if no symptoms are present. The correct diagnosis should thus be made with the available imaging modalities. We reviewed our series of 11 bronchogenic cysts, all of them studied with conventional radiology (CR), as well as with such newer imaging modalities as CT and/or MRI. All mediastinal lesions had fluid density at CT and were homogeneously hyperintense on T2-weighted MR images. On the contrary, on T1-weighted images, some lesions were hypointense and some hyperintense, probably because of their rich protein content. In contrast, hilar or pulmonary lesions had air inside, except for one case--characterized by multiple localizations--in which the hilar lesion exhibited the same fluid density as the mediastinal lesions. The CT or MR finding of a lesion with fluid content below the carina permits a nearly unquestionable diagnosis of bronchogenic cyst since the other cystic lesions involve this region very rarely. In all the other cases, other types of mediastinal or hilar-pulmonary lesions cannot be ruled out. In particular, in case of cysts in paraesophageal site, no imaging modality permits to differentiate bronchogenic from enteric cysts; in some cases, the differential diagnosis may be impossible even with histology of the resected specimen.