Contrast magnetic resonance imaging diagnosis of periaortic bronchogenic cyst.

A 39-year-old woman who had suffered from intermittent left back pain for 7 months was diagnosed as having a tumor in the posterior mediastinum to the left of the seventh thoracic vertebra. It was attached to the descending aorta and to a rib. Preoperative contrast magnetic resonance imaging strongly suggested that the tumor was a cystic lesion. We resected the tumor, and it was revealed to be a bronchogenic cyst. After 7 months' follow-up, the patient is asymptomatic and without complications. Bronchogenic cysts are rare developmental abnormalities of the primitive foregut and seldom arise in the posterior mediastinum, especially in a periaortic position. The preoperative diagnosis is difficult because of the diverse nature of a cyst's contents. We were able to predict preoperatively the nature of the tumor and its relation to other structures. Contrast magnetic resonance imaging is helpful in elucidating these cysts.