This patient has a large mass in the middle mediastinum. The differential diagnosis for such a mass includes:

• lymphoma or other lymphadenopathy
• lung cancer
• aortic aneurysm or other vascular abnormality
• abscess
• hematoma
• esophageal carcinoma, esophageal duplication cyst
• metastatic disease
• hiatus hernia
• bronchogenic cyst
This elderly patient complained of gastroesophageal reflux symptoms. This clinical history, plus the presence of an air-fluid level within the mass suggests a hiatus hernia.