Diagnosis of benign cysts of the mediastinum: the role and risks of EUS and FNA

BACKGROUND: Benign mediastinal cysts, which account for approximately 20% of mediastinal masses, may be diagnostic challenges. Information regarding the use of EUS and EUS-guided FNA in this setting is limited. The aim of this study was to demonstrate the value and potential risks of EUS and EUS-FNA in the diagnosis of mediastinal foregut cysts. METHODS: The EUS database of a single tertiary referral center was reviewed for the diagnosis of benign mediastinal cysts. Twenty patients were identified who underwent 23 EUS examinations for suspected mediastinal cysts (n = 4), for follow-up of a known cyst (n = 3), or for a mediastinal mass of unknown origin (n = 16). RESULTS: In 19 patients, the definite diagnosis of a mediastinal cyst was established by EUS. Twelve cysts appeared anechoic, 6 were hypoechoic, and one anechoic cyst contained small echoic foci. CT (n = 17) or magnetic resonance imaging (n = 1) was performed in 18 cases; only 4 of these were diagnostic of a cyst. In 3 cases, the cyst contents were aspirated by EUS-FNA. In a fourth case, a solid-appearing duplication cyst, misdiagnosed by EUS, was sampled with FNA and core biopsy. This patient developed severe sepsis secondary to mediastinitis 4 days later. Thoracotomy revealed an infected bronchogenic cyst. CONCLUSIONS: EUS provides a minimally invasive approach to the diagnosis of benign mediastinal cysts and may be more accurate than CT or other imaging modalities. Aspiration of suspected cysts should be undertaken with caution, given the risk of infection.