ABSTRACT
Congenital pulmonary airway malformation (CPAM) occurs most commonly in infants. It is divided into 5 types. The most common types 1 and 2 are cystic, type 0 presents as bronchial buds without alveolar tissue, most likely corresponding to alveolar dysgenesis, while type 3 is composed of branching bronchioles and appears as a solid lesion. A defect in the epithelial-mesenchymal crosstalk might be the underlying mechanism for all. Type 4 is a peripheral cystic lesion with a thin cyst wall covered by pneumocytes. CPAM 4 has been mixed up with pleuropulmonary blastoma (PPB) type I and some authors question its existence. We investigated five cases of CPAM type 4 for the presence or absence of rhabdomyoblasts, and for markers associated with CPAM development. In addition, all cases were evaluated for mutations within the Dicer gene and for mutations of the RAS family of oncogenes. All five cases showed smooth muscle actin and desmin-positive cells; however, only one case showed a few cells positive for MyoD. The same case showed a mutation of Dicer 1. All cases were negative for mutations of the RAS family of genes. Fibroblast growth factor 10 was similarly expressed in all cases, and thus cannot be used to differentiate CPAM4 from PPB-I. Low expression of the proliferation marker Ki67 was seen in our CPAM 4 cases and the probable PPB-I case. YingYang-1 protein seems to play an active role in the development of PPB-I. CPAM 4 can be separated from PPB-I based on the presence of rhabdomyoblasts and mutations in Dicer 1 gene. These cells might not be numerous; therefore, all available tissue has to be evaluated. As CPAM 4 morphologically looks very similar to PPB-I, it might be speculated, that there exists a potential for progression from CPAM 4 to PPB-I, by acquiring somatic mutations in Dicer 1.
Subject(s)
Cystic Adenomatoid Malformation of Lung, Congenital/pathology , DEAD-box RNA Helicases/genetics , Pulmonary Blastoma/etiology , Pulmonary Blastoma/genetics , Ribonuclease III/genetics , Adolescent , Biomarkers, Tumor/genetics , Cystic Adenomatoid Malformation of Lung, Congenital/complications , Cystic Adenomatoid Malformation of Lung, Congenital/diagnosis , Diagnosis, Differential , Disease Progression , Female , Genes, ras , Humans , Infant , Lung Neoplasms/pathology , Male , Middle Aged , Mutation/genetics , Young AdultABSTRACT
Congenital pulmonary airway malformation (CPAM) is a developmental disorder. Types 1-2-3 are the more common ones. Atypical goblet cell hyperplasia (AGCH) in CPAM might be a precursor lesion for pulmonary adenocarcinomas. In nine out of 33 CPAM cases, types 1-3 showed foci of goblet cell proliferations. As these cells completely replace normal epithelium, we prefer to name these proliferations AGCH. In 5 cases, adenocarcinomas were seen (AC). All cases were analyzed for proteins possibly being associated with CPAM development: fibroblast growth factor 10 (FGF10) and receptor 2 (FGFR2), forkhead box A1 (FOXA1) and A2 (FOXA2), MUC protein 5AC (MUC5AC), human epidermal growth factor receptor 2 (erbB2, HER2/neu), hepatocyte nuclear factor 4α (HNF4α), SOX2, and Ying Yang protein 1 (YY1). By next generation sequencing, AGCH and adenocarcinomas were evaluated for driver mutations. Expression for FGF10, FGFR2, FOXA1, and FOXA2 was seen in CPAM epithelium and stroma, but not differently in AGCH and AC. SOX2 was positive in CPAM epithelium and AGCH, however weakly in AC. YY1 and MUC5AC showed more intense staining in AGCH and AC than in CPAM epithelium. HER2 was intensely expressed in AC and less intensely in AGCH, but not in CPAM epithelium. KRAS mutation in exon 2 was detected in all AGCH and AC, but was absent in CPAM epithelia. AGCH can arise in CPAM types 1-3. Oncogenic KRAS mutation seems to be the oncogenic driver already in AGCH, proving its role as a precursor lesion for adenocarcinoma. It might upregulate HER2 at the protein level. YY1 seems to be involved in carcinogenesis.
