Spontaneous pneumothorax in cystic adenomatoid malformation. Unusual clinical and histologic features.

Pneumothorax is a rare presentation of congenital cystic adenomatoid malformation (CCAM) in the newborn period and is presumed to be due to resuscitative measures. A previously well three-week-old baby presented with spontaneous tension pneumothorax due to CCAM. In the lung resection specimen, a malformation was seen, which in addition to the histologic changes of CCAM, showed diffuse vascular proliferation in the interstitium and lining of air space by type 2 pneumocytes. We propose that this is a new variant of CCAM rather than one of the classic three types. The unusual clinical manifestation may be related to the unusual histologic features.