C45-03 The Pleura (Plot) Thickens: A Remarkably Large Pleural-Based Bronchogenic Cyst

Introduction Bronchogenic cysts are uncommon lesions that are born from the foregut as part of the cleavage between the digestive tube and respiratory track during embryogenesis. Depending on when in development they originate, these cysts can appear in various places, such as in the mediastinum or within the lung parenchyma. Cysts formed later in development tend to form more peripherally in the lungs and are often recognized early in life. Ultimately, it can be difficult to attribute all BC to congenital defects if discovered later in life; some pathologies can mimic cystic formations. In our literature review, retrospective studies have been done to both define typical CT appearance, locations and sizes - these lesions are more commonly located within the lung parenchyma/subpleural. On CT, there can be some degree of fluid attenuation or air component and can also be described as soft tissue densities. It can be difficult to correctly diagnose these lesions with certainty preoperatively with CT imaging alone. Case Here we present a patient with a 15.8 x 12.1 x 15.4 cm pleural based soft tissue density with scattered peripheral calcification and close abutment of the right and left atria. This lesion was measured on a CT scan in 2018 as 14.4 x 10.8 x 11.2 cm, but had now rapidly grown in size. The patient was without complications such as pleural effusion or major symptomatology in 2018. A BC was suspected based on imaging, though the HU (28) was also suggestive of an alternative soft tissue density including lipoma, and the pleural based location was certainly uncommon for a BC. The patient ultimately underwent a right thoracoscopy with complete pulmonary decortication. Intraoperative surgical pathology revealed that this lesion was a bronchogenic cyst. The patient’s hospitalization was complicated by a lack of lung reexpansion, the need for multiple chest tubes, and a persistent air leak. The patient was successfully discharged after a month long hospitalization. Discussion On literature review, a 2023 study investigated 136 patients with bronchogenic cysts with the largest measuring 14cm with a mean of 4.4cm across all patients. This case demonstrates an extraordinarily large 15cm bronchogenic cyst with a rare pleural-based location, a moderately fast progression in size with mass effect with encroachment on the atria, and a diagnosis ultimately requiring biopsy given the difficulty of assessment with CT imaging alone. This abstract is funded by: none