Background and study aims Tumor seeding after endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is rare. A 53-year-old man underwent transesophageal EUS-FNA for diagnosis of a 6-cm mass in the mediastinum as seen by computed tomography (CT). Four weeks later, repeat CT scan revealed a mass in the esophageal wall. Upper gastrointestinal endoscopy confirmed a lesion in the mid-esophagus, which was biopsied and found to be consistent with needle tract seeding after EUS-FNA. Tumor seeding in the gastrointestinal wall or peritoneum after EUS-FNA is rare, but may adversely affect the prognosis. Indications for EUS-FNA must be carefully considered.