Table 4. – Pathology of congenital pulmonary airway malformation (CPAM) Type 0 Type 1 Type 2 Type 3 Type 4 Relative frequency % v2 w65 10–15 v5 10–15 Lesion weight g 20–40 15–50 3–15 20–90 15–100 (age dependent) Size of largest cysts cm# 0.5 10 2.5 1.5 (if liveborn) 15 (in older patients) Epithelial (mucosal) lining of cysts CPTC, tracheal like CPTC, bronchial like Tall columnar, bronchiolar like Cuboidal Type 1 and 2 alveolar lining cells Mucogenic cells All cases 35–40% along epithelial lining Absent Absent Absent Composition of wall beneath mucosa Resembles peribronchial tissue of hilum Thick submucosal muscular band Thin peribronchiolar tissue Alveolar septal-like tissue Thin-to-thick mesenchymal tissue Cartilage plates All cases 5–10% of cases Absent Absent Rare Vasculature Prominent arteries and veins Pulmonary arteries resembling those of bronchovascular bundle Small arteries and arterioles Only rare thin-walled venous structures Large thick-walled arteries to delicate alveolar septal capillaries CPTC: ciliated pseudostratified tall columnar.:# maximum diameter. J.T. STOCKER, A.N. HUSAIN 4