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.
Highlights
Congenital pulmonary airway malformation (CPAM) is a rare disease of the lung
Four-micrometer thick sections were prepared from all available paraffin blocks and incubated with antibodies for smooth muscle actin (SMA), desmin (DES), and MyoD, to characterize smooth muscle cells, myofibroblasts, and rhabdomyoblasts
We investigated five cases, which have been diagnosed as CPAM type 4 based on the published criteria of multiple large peripheral cysts covered by pneumocytes and thin-walled stroma
Summary
Congenital pulmonary airway malformation (CPAM) is a rare disease of the lung. The incidence rate is between 1:11000 and 1:35000 in newborns [1, 2]. Due to the ongoing improvements in prenatal ultrasound technology, most of the cystic malformations are detected intrauterine [3, 4]. This might explain, why the incidence of CPAM continues to rise. CPAM, CPAM type 4 is a peripheral cystic lesion, defined as a defective growth of distal alveoli. The stroma of CPAM 4 has not been thoroughly investigated [8,9,10,11]
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