Novel Classification of Congenital Cystic Lung Disease

The classification of congenital cystic lung disease (CCLD) has been confusing for many years, mostly because the clinical entities included in the previous classifications are not independent mutually and there are many overlapping or “hybrid lesion” of the different entities seen in the clinical practice. In order to solve these problems, a novel classification of CCLD was recently proposed in Japan based on the results of the nationwide survey of CCLD, the pathological review, and the systematic review of the literatures. The new classification divides CCLD into five major entities according to the embryology how the lesion is formed during the development of the lung: (1) pulmonary airway malformation; (2) lung bud malformation; (3) foregut malformation; (4) bronchial atresia; and (5) others. To avoid overlapping of each entity of CCLD, the diseases included in each entity are defined only by the lesions primarily formed during the pulmonary development. Thus, the term “hybrid lesion” is abandoned, and the exclusion criteria is prescribed strictly. The present classification redefines each entity of CCLD more clearly and aims to correlate the clinical feature and pathological diagnosis more closely. The novel classification is presented and explained in this chapter.