Clinical features of atypical solid-type congenital pulmonary airway malformation (CPAM) type 1.

Introduction: Type 1 congenital pulmonary airway malformation (CPAM) is characterized by large, dilated cysts that rapidly expand due to aeration immediately after birth, often necessitating surgical resection. In atypical cases of CPAM type 1, fetal T2-weighted magnetic resonance imaging (MRI) reveals a low-intensity solid lung mass containing multiple irregular T2 high-intensity areas.

Methods: Data were retrospectively collected for infants with atypical CPAM type 1 born at our hospital between March 2002 and December 2022.

Results: Four infants were identified, all presenting with a low-intensity solid lung mass on T2-weighted fetal MRI and requiring respiratory support after birth. Chest X-rays showed reduced aeration within the mass. Three infants with CPAM volume ratios (CVRs) ≥1.6 underwent emergency surgery on day 1 or 2 due to respiratory failure, while the fourth infant had elective surgery on day 9. Histological examination revealed small CPAM type 1 cysts (inner diameter [I.D.] 1-10 mm), lined by ciliated columnar epithelium and surrounded by a solid component composed of proliferative mucous cells and smaller cysts (I.D. 0.1-0.6 mm), lined by ciliated low-columnar or cuboidal epithelium resembling CPAM type 2 cysts.

Conclusion: We managed four cases of solid-type CPAM type 1 with consistent findings on fetal MRI, chest X-ray, and histology. Larger CVRs were associated with the need for early neonatal surgery. Given the volumetric effect on surrounding lung tissue, early surgical resection may be required for large lesions.