Abnormal lung morphology Pulmonary hyperplasia 2025-05-03T09:32:30Z Pulmonary Hyperplasia is an absolute increase in the number of alveoli, which are mildly enlarged. Pulmonary hyperplasia has been also referred to as polyalveolar lobe and type 3 cystic adenomatoid malformation. The pathogenesis and clinical characteristics of pulmonary hyperplasia are related to congenital lobar overinflation/emphysema, but should be distinguished. In the latter condition, the volume increase is due to alveolar enlargement as opposed to an absolute increase in alveoli. Radial alveolar counts can be helpful for distinguishing between these two abnormalities. Pulmonary hyperplasia may be associated with in utero death due to compression of venous return to the heart and/or esophageal compression, resulting in polyhydramnios and fetal hydrops. The therapy for infants with lobar distension causing severe mediastinal shift and normal lung compression is surgical removal of the affected lobe or segment.