Large Thymic Cyst Presenting with Stridor and Syncope: A Diagnostic and Therapeutic Challenge

He was admitted to the Respiratory Intensive Care Unit and managed with noninvasive ventilation and high-flow nasal cannula.A large thymic cyst was identified as a cause of stridor as symptoms were more marked in supine position than lateral decubitus.Due to multiple comorbidities, he was a poor surgical candidate.After discussion with interventional radiologist, USGguided pigtail catheter insertion (Fig. 2D) and drainage of the mediastinal lesion were performed.The aspirated fluid was clear and acellular, with glucose 66 mg/dL, protein 420 mg/dL, adenosine deaminase (ADA) 1.41 U/L, and lactate dehydrogenase (LDH) 4 IU/L, which suggests exudative nature of fluid.These findings supported the diagnosis of a benign thymic cyst.In total, 1.5 L of fluid was aspirated over 3 days.The patient showed significant improvement in dyspnea, syncope, and stridor, and postprocedure chest X-ray showed complete resolution of the lesion (Fig. 1B).An alcohol-based sclerosant was instilled into the cyst before removal of pigtail catheter.