Pleuropulmonary Blastoma in Children: A Nationwide Multicenter Study

<b>Background/Objectives</b>: This study involved an analysis of clinical data, histological types, genetic predisposition, treatment and outcomes in PPB in children. <b>Patients and methods</b>: We conducted a retrospective review of children treated for PPB at Polish pediatric oncology centers between 2011 and 2024. <b>Results:</b> A total of fifteen children (seven boys, eight girls; median age of 39 months; range: 27-64 months) were included. Type II solid/cystic PPB and type III solid PPB were diagnosed in six and eight children, respectively (one not known). Overall, 93% of patients were diagnosed at up to 4 years of age. Metastatic disease at diagnosis was confirmed in three (20%) patients, localized in bones, bone marrow and lymph nodes. Diagnosis was confirmed via central pathology review in 11 patients (73%). DICER1 pathogenic variants were identified in eight patients. All children presented with respiratory symptoms. The tumor dimensions were >10 cm (n = 7), 5-10 cm (n = 5) and <5 cm (n = 2). No bilateral lung involvement was observed. Tumor biopsy was performed in six children (40%), with subsequent resection (R0) in five patients. Primary resection (R0) was achieved in three patients (20%) with type II (n = 1) or type III (n = 2). In the other six patients, non-radical resection was performed: R1 in four (27%) children (with a tumor rupture in one patient) and R2 (subtotal resection) in two children (13%). All patients received postoperative chemotherapy. Maintenance chemotherapy was given to two patients. No patient received radiotherapy as first-line treatment. Progressive disease occurred in two patients in the CNS and lungs. Relapsed disease appeared in three patients, all with CNS involvement. <b>Conclusions</b>: PPB is a rare, malignant tumor of early childhood with an uncertain prognosis. Despite multimodal treatment, patients remain at risk of progression or CNS relapse. Complete surgical resection remains a key prognostic factor.