Congenital cystic adenomatoid malformation

The greatly expanded right upper lobe is outlined by arrows. A section has been taken (next slide). Secondary hypoplasia of the left lung is apparent. The cause of this disorder is unknown. The lesion sometimes is discovered by ultrasound in the hydropic fetus.

Cysts can be absent or of variable size from large and grossly visible to microscopic. In this section one sees cysts lined by cuboidal or ciliated epithelium on thickened fibrous septa.

Congenital Cystic Adenomatoid Malformation is a hamartomatous lesion of the lung with abnormal proliferation of tissue of the distal bronchus and parenchymal tissue. This tissue retains normal connections to the respiratory tree and pulmonary vascular bed. Some prefer the term Congenital Pulmonary Airway Malformation because not all lesions are cystic. This abnormality usually presents in fetal or neonatal life. The diagnosis is now usually made by fetal ultrasonography. Some lesions have been observed to spontaneously regress. Stillbirth or perinatal respiratory distress can occur. Mediastinal shift, polyhydramnios, pulmonary hypoplasia, and/or hydrops fetalis can be noted.