Intrapulmonary Bronchogenic Cyst Adjacent to the Inferior Pulmonary Ligament Mimicking a Paraesophageal Mediastinal Cyst: A Case Report.

Bronchogenic cysts are rare congenital foregut malformations that most commonly arise in the mediastinum. Intrapulmonary bronchogenic cysts are less frequent and may present diagnostic challenges when located adjacent to mediastinal structures. We report a case of an intrapulmonary bronchogenic cyst that closely mimicked a paraesophageal mediastinal cyst on preoperative imaging. A 72-year-old man was referred to our department after a cystic lesion was incidentally detected during a routine health examination. CT demonstrated a 37-mm well-circumscribed cystic lesion in the right lower thorax. The lesion was located between the esophagus, inferior vena cava, vertebral body, and diaphragm. MRI revealed a well-circumscribed cystic lesion with features suggestive of benignity. Based on these findings, a mediastinal bronchogenic cyst or esophageal duplication cyst was suspected. Uniportal video-assisted thoracoscopic surgery was planned for resection of the presumed mediastinal cyst. Intraoperatively, the lesion was found to originate from the right lower lobe adjacent to the inferior pulmonary ligament rather than from the mediastinum. Wedge resection of the affected lung was performed through a single 4-cm incision. Histopathological examination demonstrated ciliated respiratory epithelium, bronchial glands, and cartilage, confirming the diagnosis of an intrapulmonary bronchogenic cyst. The postoperative course was uneventful. This case highlights the difficulty of accurately determining the anatomical origin of cystic lesions arising adjacent to the inferior pulmonary ligament. Intrapulmonary bronchogenic cysts should be considered in the differential diagnosis of paraesophageal mediastinal cysts, particularly when lesions are located near the inferior pulmonary ligament, even when CT and MRI findings strongly suggest a mediastinal origin.