Diagnosis of mediastinal cysts: the role and safety of EUS-FNA with 19-gauge needle: a retrospective cohort study

Background: Mediastinal cysts are uncommon, and their diagnosis remains a clinical challenge, especially for patients with a solid mass on computed tomography (CT). Endoscopic ultrasound (EUS) is considered a valuable method to differentiate mediastinal cysts and EUS-fine needle aspiration (FNA) is a strategy for obtaining specimens from the cysts for cytological diagnosis. This study aims to evaluate the safety and utility of EUS-FNA for diagnosis of mediastinal cysts. Methods: This was a retrospective analysis of patients who underwent EUS-FNA with 19-gauge needle at Tianjin Medical University Cancer Institute and Hospital and were further diagnosed with mediastinal cysts confirmed by cytological and surgical pathological results between January 2016 and December 2020. Safety was estimated by the incidence of reported adverse events (AEs). Patients were followed for 48 hours and 1 week after the EUS-FNA procedure to evaluate AEs. Results: A total of 20 patients were diagnosed with mediastinal cysts using EUS- FNA, yet only 5 were diagnosed by CT. There were 15 patients diagnosed with bronchogenic cyst, 4 with enteric cyst, and 1 with pericardial cyst. The EUS appearance of cyst content varied, ranging from anechoic (4 cases) to hypoechoic (16 cases). AEs occurred in 2/20 (10%) patients after the EUS-FNA indicating an acceptable low rate of AEs. For all anechoic cysts that underwent complete FNA drainage, 3 patients had good prognosis, whereas 1 experienced recurrence. For 16 patients with hypoechoic cysts, adequate tissue was obtained for cytological examination. No patient developed an infection-related complication. Conclusions: For the diagnosis of mediastinal cysts, EUS-FNA was more accurate than CT. The EUSFNA of mediastinal cysts is safe with an acceptable low rate of AEs when antibiotic prophylaxis is used postoperatively. Cysts containing free-flowing fluid can be achieved with complete needle drainage by a single pass with a 19-gauge needle.