Infectious Risk Enhanced Because of Endobronchial Ultrasound-guided Transbronchial Needle Aspiration of Bronchogenic Cysts

To the Editor: Bronchogenic cysts are rare congenital lesions, and account for approximately 10% of mediastinal masses in adults.1,2 Most bronchogenic cysts produce no symptoms and are discovered accidentally on the chest radiographs. The typical computed tomography (CT) appearance of a bronchogenic cyst is an oval or round soft-tissue mass in a paratracheal or mediastinal location. Although a CT scan can detect the mediastinal cysts, they can frequently be misinterpreted as solid lesions. The cysts usually have a thin wall and the margins are well defined. The contents of the cysts are of low attenuation on a CT scan and cannot be enhanced with a contrast agent. The definitive histologic diagnosis can only be made through surgical excision. A 56-year-old asymptomatic woman was accidentally found to have “mediastinal lymphadenopathy” by a chest CT examination that showed a 2.4×4.3-cm lesion posterior to the superior vena cava and ascending aorta (corresponding to the station 4 lymph nodes) (Fig. 1). She was referred for endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) for the diagnosis. EBUS showed a hypoechoic lesion adjacent to the superior vena cava with well-defined sonographic margins (Fig. 2), and it was misinterpreted as lymphadenopathy and sampled by single pass of EBUS-TBNA. Clear yellow fluid was obtained using a negative-pressure syringe. Streptococci viridans was isolated by culture from the drained fluid. The patient reported no fever or chest pain after the examination. There was no CT evidence of infection of the mediastinal cyst. Intravenous cefperazone-sulbactam (3 g, twice daily) was prescribed prophylactically for 10 days. Repeat CT, 20 days after the EBUS-TBNA, showed no change in the size of the cyst, with the CT attenuation value of 9 to 16 Hounsfield units.FIGURE 1.: Computed tomography scan showing a mass posterior to the superior vena cava and ascending aorta. FIGURE 2.: Endobronchial ultrasound showing a hypoechoic lesion adjacent to the superior vena cava. Endoscopic ultrasound has been used as a minimally invasive approach to establish the diagnosis of benign mediastinal cysts.3,4 Under an ultrasound, a cyst appears like a hypoechoic mass with clear sonographic borders, so the ultrasound is very useful in distinguishing cystic and solid lesions. Drainage of fluid by esophageal ultrasound-guided fine-needle aspiration also confirms the diagnosis of mediastinal cysts; however, risk of infection could preclude it from routine use as reported earlier.4,5 Traditionally, surgical resection has been recommended as the first-line treatment option for symptomatic patients. Until recently, only 1 case of a bronchogenic cyst, which was diagnosed and treated successfully using EBUS-TBNA, was reported.6 In our case, the diagnosis of a bronchogenic cyst was established unexpectedly by drainage of the fluid through EBUS-TBNA. Although the patient did not develop infection of the bronchogenic cyst after using antibiotics, we think EBUS-TBNA increases the infection risk. Positive culture of the drained fluid showed that the TBNA needle might have been contaminated by the bacteria colonized in the oropharynx. This could certainly be a case of pseudoinfection; however, we suggest that EBUS-TBNA should be used prudently as a diagnostic and therapeutic tool for bronchogenic cysts as it might be associated with an increased risk of infection. Qing Tian, MD Liang-An Chen, MD, PhD Hong Hu, MD, PhD Department of Respiratory Diseases PLA General Hospital Beijing, China