Thoracic metastasis of a pediatric posterior fossa group A ependymoma: a rare case and literature review.

Ependymomas are rare central nervous system tumors, with posterior fossa group A (PFA) ependymomas representing an aggressive pediatric subtype. While cerebrospinal fluid dissemination is well recognized, hematogenous spread and extracranial metastasis remain exceedingly rare and poorly understood. A 7-year-old child presented with symptoms of increased intracranial pressure and was found to have a mass in the fourth ventricle. Histopathology confirmed an ependymoma with features of the PFA subtype, including high marker of proliferation Kiel 67 index, glial fibrillar acidic protein and epithelial membrane antigen positivity, loss of trimethylation of lysine 27 on histone H3 and chromosome 1q gain (three copies). The patient underwent subtotal resection followed by craniospinal radiotherapy, local boost and six cycles of adjuvant chemotherapy with cisplatin, temozolomide and bevacizumab. Subsequently, progressive respiratory symptoms led to the discovery of pleural effusion and mediastinal metastases. Thoracoscopic biopsy confirmed metastatic ependymoma with immunophenotypic concordance to the primary tumor. Management included systemic chemotherapy, surgical resection and localized thoracic radiotherapy. This case reveals the rare occurrence of extracranial metastasis in pediatric PFA ependymoma and emphasizes the challenges of incomplete resection and atypical dissemination. A focused review of 14 pediatric PFA ependymoma cases highlights the importance of molecular profiling, close surveillance and recognition of non-traditional metastatic pathways in high-risk disease.