From cystic pulmonary airway malformation, to bronchioloalveolar carcinoma and adenocarcinoma of the lung.

Bronchioloalveolar carcinoma (BAC) of the lungs is a known morphological subtype of nonsmall cell cancer. The current study presents several carcinogenetic theories of BAC and the possible relationship with atypical adenomatous hyperplasia and congenital pulmonary airway malformation (CPAM). The authors present an unusual case of BAC developed in an area of CPAM, with subsequent progression to metastatic adenocarcinoma (AC). The case is unique due to the combination of: early age of presentation; neoplastic transformation of a CPAM; unaltered course over 15 yrs; and its particular pattern of slow morphogenesis and degeneration into an invasive AC of the lung. The case also presents the unique features of a long-standing, unaltered natural course of paediatric BAC towards invasive and metastatic AC, illustrating that lack of growth over many years cannot be entirely trusted as a criterion of benignity. In conclusion, clinicians and pathologists need to be aware of the fact that congenital pulmonary airway malformation so far represents the only known pre-invasive lesion for mucinous bronchioloalveolar carcinoma.