A teenager with lung mucinous adenocarcinoma harboring a KRAS mutation arising in type 1 congenital cystic adenomatoid malformation (CCAM)

A 14-year-old boy was referred to our hospital with a 1-year evolving productive cough and hemoptysis.A Positron-emission-tomography scan (PET/CT) revealed a 17cm hypermetabolic right lower-lobe lung mass in contact with mediastinal structures as well as multiple bilateral pulmonary nodules. Percutaneous lung biopsy identified an invasive mucinous adenocarcinoma (IMA; formerly mucinous BAC) associated with Type I Congenital Cystic Adenomatoid Malformation (CCAM).Genomic profiling was performed and detected a KRAS mutation (G12D).

NSCLC can be rarely seen in young patients. In the pediatric population, the incidence is approximately 0.0002% and it is usually associated with a congenital malformation.

CCAM is a group of rare lung congenital malformations. The estimated incidence is 1 in 25.000 to 1 in 35.000 pregnancies and it represents 25% of all congenital lung malformations. Type I is the most common subtype of CCAM. It is characterized by the presence of large cysts lined by pseudostratified ciliated cells that are often interspersed with rows of mucous cells.It has been largely recognized that some cases of type I CCAM show malignant transformation to mucinous adenocarcinoma.

Recent data clearly demonstrated that the occurrence of mucinous adenocarcinoma in type I CCAM is associated with KRAS mutation.

This case highlights the relationship between type I CCAM and lung mucinous adenocarcinoma/KRAS mutant. Moreover, demonstrated that the clinical outcome was consistent with the molecular feature of a KRAS mutant patient.