Multifocal synchronous mucinous adenocarcinomas arising in congenital pulmonary airway malformation: a case report with molecular study.

Aims Congenital pulmonary airway malformation (CPAM) is a rare developmental anomaly of the lung. Here, we report a case of mucinous adenocarcinoma arising in CPAM. A 23-month-old boy underwent a thoracoscopic lobectomy of the left upper lobe of the lung based on a presumptive diagnosis of asymptomatic CPAM, found in antenatal sonogram. Methods and results Histologically, the lesion was consistent with CPAM, Stocker type I. In addition, multiple foci ranging from mucinous epithelial hyperplasia to mucinous adenocarcinoma were detected. All lesions shared the same immunoprofile with the expression of cytokeratin (CK) 20, MUC5AC, and human epidermal growth factor receptor2 (HER2), but were negative for CK7, transcription factor 1 (TTF-1), MUC1, CDX2, BRAF (VE1) and anaplastic lymphoma kinase (ALK). K-RAS point mutation (G12V) was also detected in all micro-dissected mucinous lesions but EGFR mutation was not found. All lesions were consistent with mucinous adenocarcinoma. The patient's clinical course has been uneventful during the 12-months follow-up period. Conclusions This interesting case demonstrated that multiple foci in CPAM can synchronously transform into malignancies.