Bronchogenic cyst. Unexpected finding in a large aneurysm of the pars membranacea septi

Intracardiac bronchogenic cysts are rare, with only 5 cases reported to date: 2 in the atrial septum, 1 in the left atrium, and 2 in the right ventricle. They are identified by asymptomatic occasional findings or nonspecific symptoms, mostly in the second to fourth decades. Bronchogenic cysts are believed to represent a localized portion of the tracheobronchial tree that separates from the normal airways during the branching process and does not undergo further development. They develop between the 26th and the 40th day of intrauterine life, during the most active period of airway development. The timing of the abnormal budding may determine the location: earlier in the mediastinum and later within lung tissue, which are the 2 most common locations. Intracardiac location can be explained with a more precocious abnormal budding, approximately 21 days after fertilization, when the cardiac primordial tube is near the foregut or primitive tracheobronchial tree. Other noncardiac, atypical locations are cutaneous, retroperitoneal, cervical, intradiaphragmatic, intrapericardial, intraspinal, and intrapleural. We report a case of a bronchogenic cyst located in the wall of a large aneurysm of the pars membranacea septi triggering premature ventricular complex (PVC) and sinus tachycardia.