You are in: eMedicine Specialties > Radiology > CHEST Bronchogenic CystArticle Last Updated: Aug 14, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 9
  Author: Eric Goodman, MD, Clinical Assistant Professor, Department of Radiology, UCSD Medical Center Eric Goodman is a member of the following medical societies: American Roentgen Ray Society, North American Society for Cardiac Imaging, and Radiological Society of North America Editors: Kitt Shaffer, MD, PhD, Director of Undergraduate Medical Education, Associate Professor, Department of Radiology, Cambridge Health Alliance; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Eric J Stern, MD, Director of Thoracic Imaging, Professor of Radiology and Medicine, Departments of Radiology and Internal Medicine, Harborview Medical Center, University of Washington School of Medicine; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Barry H Gross, MD, Professor, Department of Radiology, University of Michigan Medical School; Professor, University of Michigan Cancer Center Author and Editor Disclosure Synonyms and related keywords: foregut cyst, duplication cyst, congenital cyst INTRODUCTIONSection 2 of 9
  BackgroundBronchogenic cysts are congenital in nature. They are part of a spectrum of congenital abnormalities of the lung, including pulmonary sequestration, congenital cystic adenomatoid malformation, and congenital lobar hyperinflation (emphysema). PathophysiologyBronchogenic cysts develop from an abnormal budding of the ventral foregut between the 26th and 40th week of gestation. As such, they are often more appropriately termed foregut duplication cysts. FrequencyUnited StatesThe frequency of bronchogenic cysts is unknown, presumably because most patients are asymptomatic. Numerous studies have documented the rare incidence of bronchogenic cysts, with the average incidence being 20 cases over a 20-year period. InternationalInternational frequency is unknown. Mortality/MorbidityAlthough bronchogenic cysts are usually an incidental finding, morbidity associated with bronchogenic cysts has been reported as occurring because the cyst becomes secondarily infected or because postobstructive pneumonia occurs. Dysphagia and dyspnea have resulted from compression of a large cyst on the esophagus and airways. Cases have been reported of cyst rupture and hemorrhage within the cyst. RaceThe frequency in different races is unknown. SexFrequency in each sex is unknown. AgeBronchogenic cysts are congenital lesions. Large cysts may present in the pediatric population because of compression of the esophagus or trachea or because of infection. In adults, the cysts typically present as an incidental mass in either the mediastinum or the lung. AnatomyBronchogenic cysts are located most commonly in the mediastinum (85%). Other common locations include subcarinal, paratracheal, and retrocardiac sites. Intrapulmonary bronchogenic cysts are less common (15%). Histologically, cysts are thin walled, filled with mucoid material, and lined with columnar respiratory epithelium, mucous glands, cartilage, elastic tissue, and smooth muscle. Clinical DetailsIn the pediatric population, bronchogenic cysts present as fever or difficultly breathing. Adults with bronchogenic cysts are usually asymptomatic. Patients with large mediastinal cysts may present with stridor or dysphagia resulting from a mass effect on the trachea or esophagus. Preferred ExaminationBronchogenic cysts are usually an incidental finding, and differentiating them from other pathologic conditions is important. On conventional radiographs, the appearances of mediastinal or lung masses are nonspecific and should be evaluated further using CT or MRI. Limitations of TechniquesChest radiograph is usually adequate for detecting larger mediastinal or lung masses; however, it is limited in its ability to differentiate solid masses from fluid. CT findings are characteristic when the lesion demonstrates water density. If the lesion demonstrates soft-tissue density, differentiating the cyst from lymph nodes or other solid lesions is difficult. MRI findings are usually diagnostic for mediastinal cysts. Intrapulmonary cysts are difficult to diagnose and must usually be aspirated to confirm the diagnosis. DIFFERENTIALSSection 3 of 9
Congenital Cystic Adenomatoid Malformation Hodgkin Disease, Thoracic Lung, Nontuberculous Mycobacterial Infections Lung, Primary Tuberculosis Non-Hodgkin Lymphoma, Thoracic Pulmonary Sequestration Sarcoidosis, Thoracic Solitary Pulmonary Nodule Other Problems to Be ConsideredMetastatic disease to the mediastinum
RADIOGRAPHSection 4 of 9
FindingsMediastinal cysts are visualized as a mediastinal mass on conventional radiographs. Intrapulmonary cysts usually present as a solitary pulmonary nodule unless the cyst contains air. Degree of ConfidenceOn conventional radiographs, findings are nonspecific. Mediastinal masses should be evaluated further using CT or MRI to confirm the presence of fluid. False Positives/NegativesDifficulty is encountered in determining whether the visualized mass is benign (eg, a bronchogenic cyst) or malignant. CT SCANSection 5 of 9
FindingsBronchogenic cysts are sharply marginated masses demonstrating water or soft-tissue density. Differences in attenuation result from the amount of proteinaceous fluid within the cysts. Cysts do not enhance after administration of IV contrast. A recent article from the Armed Forces Institute of Pathology documented the appearance of 62 cysts: 40% were water density, 40% were soft-tissue density, 5% contained milk of calcium, 10% were indeterminate from streak artifact, and the remainder were intrapulmonary, either completely air filled or containing an air-fluid level.1 In addition to intrapulmonary and mediastinal locations, bronchogenic cysts have been reported to be located in infradiaphragmatic areas, cutaneous areas, intrapericardial areas, and intramural areas of the esophagus. Degree of ConfidenceIn the proper clinical setting, a CT finding of a sharply marginated, nonenhancing, water-density mass is diagnostic of a bronchogenic cyst. Nonenhancing masses demonstrating soft-tissue density need further evaluation using MRI. Location is also important. Intrapulmonary cysts are usually difficult to diagnose and usually require aspiration for diagnosis. False Positives/NegativesMost bronchogenic cysts are relatively characteristic in appearance on CT, but in atypical cases with hemorrhage or infection, findings may be confused with those of necrotic adenopathy, cystic lung disease, or lung abscess. MRISection 6 of 9
FindingsBronchogenic cysts are usually bright on T2-weighted images and dark on T1-weighted images. Cysts do not enhance after administration of IV gadolinium. Degree of ConfidenceOn T2-weighted images, the brighter the cyst, the more confident the diagnosis of bronchogenic cyst. Lack of enhancement is also characteristic. Location is important in differentiating bronchogenic cysts from other cysts, such as pericardial cysts. False Positives/NegativesAs with CT scans of typical bronchogenic cysts, MRI findings are very specific and few false-positive or false-negative findings occur. For atypical cysts, the main confusion is with necrotic tumors or infections. INTERVENTIONSection 7 of 9
Occasionally, large cysts can be aspirated percutaneously for diagnostic or therapeutic indications. MULTIMEDIASection 8 of 9
REFERENCESSection 9 of 9
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