Invasive non-mucinous adenocarcinoma with hepatoid adenocarcinoma transformation arising in adult congenital pulmonary airway malformation: a case report

Congenital pulmonary airway malformations (CPAM) is a rare, non-genetic disease of unknown etiology, characterized by nodular and cystic abnormalities resulting from dysregulated airway development. Some cases may be accompanied by malignant tumors, including mucinous adenocarcinoma, rhabdomyosarcoma and pulmonary blastoma. A 73-year-old male patient was admitted to our hospital due to the presence of a pulmonary mass. Computed tomography imaging suggested the possibility of a malignant neoplasm, and the thoracoscopic lung resection was subsequently performed. Histopathological analysis revealed invasive non-mucinous adenocarcinoma arising in the type I CPAM, exhibiting typical morphological and immunohistochemical features. The tumor demonstrated focal transformation into hepatoid adenocarcinoma, with immunophenotypic expression including diffuse positivity for HepPar-1, AFP, SALL4, and GPC3, as well as aberrant β-catenin expression and SMARCA2 deficient, while SMARCA4 expression remained preserved. Targeted next-generation sequencing revealed that the tumor harbored NFE2L2 exon 2 mutation. This case expands the morphological and molecular spectrum of malignant transformation in adult CPAM.