Durable Response to Larotrectinib in a Child With Histologic Diagnosis of Recurrent Disseminated Ependymoma Discovered to Harbor an NTRK2 Fusion: The Impact of Integrated Genomic Profiling

Ependymomas comprise approximately 10 percent of childhood CNS malignancies and are associated with dismal outcomes if metastatic, incompletely resected, or recurrent.1 Standard therapy consists of maximal safe surgical resection followed by focal irradiation.2 Recurrent fusion genes involving C11orf95-RELA or YAP1 have been identified in supratentorial ependymomas, but targetable molecular lesions are rare.3,4 Here, we report a sustained response to larotrectinib in a pediatric patient with a histologic diagnosis of recurrent metastatic anaplastic ependymoma, whose molecular testing unexpectedly revealed a KANK1-NTRK2 fusion and methylation profile most consistent with pleomorphic xanthoastrocytoma (PXA). This case highlights the potentially profound clinical implications of integrating genomic profiling into the diagnostic evaluation of pediatric CNS tumors.