An initial chest x-ray showed a large cystic lucency in the left lung base with internal air-fluid level. The differential diagnosis included congenital diaphragmatic hernia, pleuropulmonary blastoma and type I congenital pulmonary airway malformation (CPAM).

A CT Chest and abdomen with contrast was ordered to further determine the pathology in the left lower hemithorax. The CT Chest showed a large thin-walled cyst measuring 30 x 50 x 31mm with air fluid level in the left lower lobe. There were no surrounding smaller cysts. CT abdomen showed intact diaphragm excluding diaphragmatic hernia. The epicenter of the large cystic lesion is located within the left lower lobe. Given this, CPAM is favored over pleuropulmonary blastoma, where the lesion location is more peripheral to the pleuropulmonary junction.

With the proposed diagnosis of CPAM, the patient underwent left thoracotomy and left lower lobectomy. The lung tissue sample morphology and immunohistochemical staining patterns supported CPAM. Pleuropulmonary blastoma is unlikely due to its characteristic cambium-like patterns of mesenchymal proliferation and rhabdomyoblastic cells not being seen.

In summary, CPAM can have a wide range of presentation and should be considered even in patients without respiratory symptoms. When determining the diagnosis of CPAM in neonates, chest radiograph is an initial starting point and enhanced chest CT is helpful in determining the diagnosis/differential diagnosis and to guide the clinical management.