Perpetual dilemma: Pleural or parenchymal/congenital or acquired solitary cystic lesion with fluid level

Congenital cystic adenomatoid malformations (CCAMs) are rare congenital, nonhereditary developmental anomalies of the lung with unknown etiology. CCAM is predominantly a disorder of infancy with the majority of the cases being diagnosed within the first 2 years of life. When CCAM presents in adults, it represents a diagnostic dilemma and requires careful evaluation. We here report a case of large solitary congenital pulmonary cystic adenomatoid malformation with infection and hemorrhage, which was diagnosed as encysted hydropneumothorax on computerized tomography scans but turned out to be infected pulmonary cystic adenomatoid malformation after surgical excision.