Congenital malformation of the pulmonary airway type IV and pleuropulmonary blastoma type I, benign, malignant or pathological expression of the same entity? Clinical case

Introduction: Congenital pulmonary airway malformation (MCAP) IV is considered a benign unilateral and multicystic lesion with a distal acinar origin and is histopathologically indistinguishable from malignant cystic pleuropulmonary blastoma (BPP) I, with an association and potential progression between the two. Case description: 28-week-old fetus with a fetal lung mass and at 7 months with a left pneumothorax, computed tomography scan with parenchymal cystic lesions; thoracotomy shows a 10 cm cystic-bullous lesion, peripherally adhered to the lower lobe and pathology with a cystic lesion of a septate cavity with abundant cuboidal epithelium with loose myxoid stroma, it is difficult to differentiate between MCAP IV and BPP I, due to being positive for the DICER1 mutation and high risk for degeneration into BPP I, a lobectomy is performed and 3 years later with a favorable evolution. Discussion: An embryonic theory has been associated, where BPP I would have its origin in an unresected MCAP IV. To distinguish between both entities we support the diagnosis of potential progression to BPP in the presence of the prenatal diagnosis, symptoms (pneumothorax), complex cyst and the DICER1 mutation.