A 51-year-old woman presented with dyspnea that had progressed over the previous year. On a physical examination, harsh, hollow breath sounds with a high-pitched timbre, termed "amphoric breathing", were identified during inspiration and expiration. Chest radiography and thoracic computed tomography performed over the previous three years revealed an enlarging cyst in the right lung arising from an area of consolidation. Pulmonary adenocarcinoma (T4 N0 M1a, stage IV) was diagnosed and considered a possible cause of the cyst, resulting in amphoric breathing.