Also called congenital cystic adenomatous malformation (CCAM), it is usually detected antenatally with a peak size at 25/40. The main risk is hydrops fetalis, with high mortality if present. If not present, spontaneous ‘resolution’ is common with 50% of babies being asymptomatic at birth. Abnormal tissue may still be present, however, with later risk of malignant transformation. Hence these babies should have postnatal CT chest with surgical resection of lesions.
Reference: Sfakianaki, A. K., & Copel, J. A. (2012). Congenital cystic lesions of the lung: congenital cystic adenomatoid malformation and bronchopulmonary sequestration. Reviews in obstetrics and gynecology, 5(2), 85.