An infected esophageal duplication cyst in a patient with non-Hodgkin's lymphoma mimicking persistent disease.

Differentiation of mediastinal cysts appearing as soft-tissue attenuation masses on computed tomography (CT) scans from malignant mediastinal masses is difficult. We report a patient with non-Hodgkin's lymphoma, who was considered to have persistent disease in the posterior mediastinum based on CT scans. However, endoscopic ultrasound (EUS) demonstrated a paraesophageal, fluid-filled cyst with echodens inclusions and no evidence of any solid component. EUS-guided fine-needle aspiration (FNA) revealed mucous, epithelial and inflammatory cells, and additionally candida albicans was cultured. Based on these findings and constant size during follow-up, the diagnosis of an infected esophageal duplication cyst was made. Thus, this report further demonstrated the impact of EUS and EUS-FNA for management of posterior mediastinal cystic lesions in selected cases.