The cyst walls are composed of fibromuscular tissue and occasional cartilage islands. Adjacent parenchyma contains smaller cysts resembling bronchioles. In the presence of chronic inflammation (lymphoid aggregates, fibrosis, macrophages, etc.), the diagnosis of Fig. 3. – Congenital pulmonary airway malformation type 1. a) Grossly, the lesion is composed of multiple interconnecting cysts. b) The cysts are lined with respiratory epithelium (ciliated pseudostratified tall columnar epithelium) overlying a wall composed of bands of smooth muscle and vascular connective tissue (haematoxylin and eosin stain). CLASSIFICATION OF CHILDHOOD CYSTIC LUNG LESIONS 7