Pleuropulmonary blastoma type I and congenital pulmonary airway malformation type 4: distinct entities or sides of the s
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COMMENTARY
Pleuropulmonary blastoma type I and congenital pulmonary airway malformation type 4: distinct entities or sides of the same coin? Giulio Rossi 1 Received: 19 March 2020 / Revised: 19 March 2020 / Accepted: 31 March 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Cystic malformations in childhood include several conditions, but congenital pulmonary airway malformations (CPAM; also known as congenital cystic adenomatoid malformations, CCAM) are the most common [1, 2]. Classification of CPAM is based on the revised clinic-pathologic criteria identified by Stocker in 2002, ranging from type 0 (acinar dysplasia) to type 4 (large peripheral thin-walled cysts lined by pneumocytes), with type I being the most frequent [3]. Type 1 and type 4 CPAM may show malignancy, namely mucinous invasive adenocarcinoma (MIA) and pleuropulmonary blastoma (PPB), respectively [4–6]. While it is widely accepted that neoplastic mucinous proliferations in type 1 CPAM derive from the transformation of glandular epithelium of the cyst through the acquisition of the same molecular oncogenic events disclosed in conventional MIA (i.e., p16 and p53 alterations, HER2 up-regulation, and KRAS mutations) [4–6], controversies still exist on the occurrence of PPB in type 4 CPAM [7]. Although rare, PPB is the most common embryonal malignant tumor of the lung in infancy and early childhood [8]. It is classified into 3 types: type I and Ir (cystic and cystic with regression, respectively), type II (cystic and solid), and type III (solid) [9, 10]. Type I PPB develops in younger age (more than 95% of less than 3 years) and is composed of cysts and septa, showing immature primitive mesenchymal cells (rhabdomyoblasts in about half of cases) underneath the low cuboidal respiratory epithelium, resulting in a cambium-like appearance [8–10]. About 70–85% of children with PPB have a heterozygous germline mutation in DICER1 gene encoding for a protein of ribonuclease III family [11–13].
* Giulio Rossi [email protected] 1
Operative Unit of Pathologic Anatomy, Azienda USL della Romagna, St. Maria delle Croci Hospital, Viale Randi 5, 48121 Ravenna, Italy
It may be difficult even for experienced pathologists to correctly identify a lesion as PPB, so a central pathology review is very helpful to clarify questionable cases [7, 9]. Indeed, it seems that the diagnosis submitted to specialized centers turned out incorrect in approximately 20% of cases [9]. In a recent study, Feinberg et al. [14] proposed a clinic-radiologic algorithm to discriminate type 1 PPB from CPAM. According to their results on 112 type I PPB and 102 CPAM, the presence of symptoms (particularly pneumothorax), multifocal lung involvement, complex cyst, and germline mutation of DICER1 gene consistently supported a diagnosis of PPB [14]. By contrast, a prenatal diagnosis together with systemic feeding vessel and hyperinflated lung were significantly associated with CPAM [14]. A careful use of this algorithm correctly distinguished PPB and CPAM in 96.7% of cases [14]. As
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