There is a large multiloculated cystic lesion centred in the right lower lobe. The multiloculations are typical for a congenital cystic adenomatoid malformation. The periphery of the lesion shows some wall thickening and ill-defined infiltration into the surrounding parenchyma which raises the possibility of some intercurrent inflammation or infection. I believe the lesion arises largely in the apical segment of the right lower lobe. The posterior medial segment shows quite striking congestion and I would suspect impaired lymphatic drainage from this segment. There is hyperinflation of the basal medial and basal lateral segment. The anterior basal segment of the lower lobe appears to have reasonably normal parenchyma. The mass effect of the cystic lesion displaces the posterior right upper lobe superiorly and displaces the hilar and the right middle lobe anteriorly. The left lung appears normal.