Solitary unilocular cyst of the lung with features of persistent interstitial pulmonary emphysema: report of four cases.

Neonatal interstitial pulmonary emphysema (IPE) is a well-characterized lesion usually presenting in preterm newborns as a complication of respiratory distress syndrome and/or assisted ventilation. Occasionally, IPE may occur spontaneously in infants with no underlying pulmonary disease. Persistence of IPE (PIPE) may be diffuse or localized. Localized PIPE usually presents as multiple cysts 0.3 to 3 cm in one or more lobes of the lung. In this report, we describe four cases of unilocular large cysts (up to 5 cm in diameter) partially lined by uni- and multinucleated histiocytes in a foreign body type reaction and showing gas dissection of the surrounding parenchyma (present in case 1). These histological features favored the diagnosis of PIPE and the cases were interpreted as such, since no other clear-cut diagnosis could be defined. However, because the lesion was limited to one lobe, and the children were full term, asymptomatic at birth and without history of respiratory distress or assisted ventilation, differential diagnosis with other pulmonary cystic lesions of infancy is mandated.