Oligodendrogliomas in pediatric and teenage patients only rarely exhibit molecular markers and patients have excellent survivals.

Although oligodendrogliomas appear histologically similar in adult and pediatric patients, the latter have only been rarely studied and most of those studies did not have long follow-up. We examined 55 oligodendroglial tumors from pediatric and teenage patients for their biomarkers with formalin-fixed paraffin-embedded tissues and studied their survival status. None of the tumors harbored 1p/19q codeletion or IDH mutation. Mutations in TERTp (4%), BRAF (11%), FGFR1 (3%) and H3F3A (5%), fusions of BRAF (8%) and FGFR1 (8%) were found sparingly and almost all in a mutually exclusive manner. Molecular events were exclusively found in tumors with classic oligodendroglial histology. Survival analysis showed remarkably excellent prognosis compared to the adult counterparts. 5-year overall survival was 95% in our cohort with median follow-up of 8.1 years and in nine patients with follow-up more than 10 years, the 10-year overall survival was 100%. The 5-year and 10-year progression-free survivals of our cohort were 89 and 77%, respectively. FGFR1 fusion seemed to confer a poor prognosis in pediatric oligodendrogliomas. Patients receiving adjuvant chemotherapy (p = 0.046) or harboring Grade II histology (p < 0.001) had longer interval to recurrence. Our study demonstrated the distinct indolent clinical course of pediatric and teenage oligodendrogliomas compared to the adult tumors. Molecular markers commonly seen in adult oligodendrogliomas and other pediatric low-grade gliomas were only rarely seen. Since there is no clinical or molecular evidence suggesting that pediatric "oligodendrogliomas" are the same as adult oligodendrogliomas albeit histologic similarity, a case can be made for their separation from adult oligodendrogliomas in the next WHO classification.