New concepts in the pathology of congenital lung malformations.

Focal developmental malformations of the lung are a heterogeneous group of lesions that display a variety of features. They often are thought to be quite distinct entities, but there is considerable overlap among these lesions. Both standard nomenclature and common usage do not identify clearly the components of these lesions in a distinctive fashion. A classification based on pathologic features is presented. A malformation sequence based on airway obstruction during development is proposed as a unifying pathogenetic mechanism for some seemingly unrelated lesions.