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.

先天性肺气道畸形（CPAM）最常见于婴儿。它分为5种类型。最常见的1型和2型是囊性的，0型表现为没有肺泡组织的支气管芽，最可能对应于肺泡发育不全，而3型则由分支性细支气管组成，表现为实性病变。上皮-间充质串扰的缺陷可能是所有人的潜在机制。4型是周围性囊性病变，其囊壁薄而被肺细胞覆盖。CPAM 4已与I型胸膜肺母细胞瘤（PPB）混合使用，一些作者质疑其存在。我们调查了5例4型CPAM的横纹母细胞的存在与否以及与CPAM发育相关的标志物。此外，对所有病例评估了Dicer基因内的突变以及癌基因RAS家族的突变。5例均显示平滑肌肌动蛋白和结蛋白阳性细胞。然而，只有一例显示出少数细胞对MyoD呈阳性。同一病例显示了Dicer 1的突变。所有病例均为RAS基因家族突变阴性。在所有情况下，成纤维细胞生长因子10的表达均相似，因此不能用于区分CPAM4和PPB-1。在我们的CPAM 4例和可能的PPB-I例中观察到增殖标志物Ki67的低表达。YingYang-1蛋白似乎在PPB-I的发展中发挥积极作用。基于横纹母细胞的存在和Dicer 1基因的突变，可以将CPAM 4与PPB-1分离。这些单元可能并不多；因此，必须评估所有可用的组织。