Adult Presentation of a Large Congenital Pulmonary Airway Malformation Discovered After Traumatic Rib Fractures.

Congenital pulmonary airway malformation (CPAM) is a rare developmental lung lesion that is usually identified prenatally or in early childhood, and adult presentations are uncommon. A 44-year-old woman presented after a fall with right-sided chest pain and dyspnea. CT chest revealed nondisplaced fractures of the right seventh through ninth ribs and incidentally identified a large multilocular cystic lesion in the right lower lobe consistent with CPAM, unchanged from imaging performed 15 years earlier. Pulmonary function testing demonstrated mild small-airway dysfunction, air trapping, and reduced diffusing capacity without restrictive physiology. Given the lesion's size and potential risk for infection or malignant transformation, the patient underwent flexible bronchoscopy followed by right muscle-sparing thoracotomy with right lower lobectomy and thoracic lymphadenectomy. Intraoperative findings included dense vascular adhesions and distorted tissue planes. The postoperative course was uncomplicated. Pathology confirmed a benign cystic congenital pulmonary lesion without malignancy. This case highlights an uncommon adult presentation of long-standing CPAM incidental discovery and underscores that radiographic stability does not exclude clinically significant disease requiring surgical management.