Clinicopathologic Features of Pediatric Oligodendrogliomas

Abstract

Oligodendrogliomas are an important adult form of diffuse gliomas with a distinctive clinical and genetic profile. Histologically similar tumors occurring rarely in children are incompletely characterized. We studied 50 patients with oligodendrogliomas (median age at diagnosis 8 y, range 7mo to 20 y). Tumors resembling dysembryoplastic neuroepithelial tumors or pilocytic astrocytomas or those having a “mixed” histology were excluded. Tumors at first diagnosis were low grade (n=38) or anaplastic (n=12). Histologic features included uniform round cells with perinuclear halos (100%), secondary structures (predominantly perineuronal satellitosis) (90%), calcifications (46%), and microcysts (44%). Sequential surgical specimens were obtained in 8 low-grade oligodendroglioma patients, with only 1 progressing to anaplasia. Studies for 1p19q performed in 40 cases demonstrated intact 1p19q loci in 29 (73%), 1p19q codeletion in 10 (25%), and 1p deletion with intact 19q in 1 (2%). Except for 2 young patients (3 and 11 y of age), patients with 1p19q codeletion were older than 16 years at diagnosis. Mutant IDH1 (R132H) protein immunohistochemistry was positive in 4 (of 22) (18%) cases, 3 of which also had 1p19q codeletion, whereas 1p19q status was not available on the fourth case. There was a nonsignificant trend for worse overall survival in grade III tumors, but no significant association with age, extent of resection, or 1p19q status. In summary, oligodendrogliomas with classic histology occur in the pediatric population but lack 1p19q codeletion and IDH1 (R132H) mutations in most instances. They are predominantly low grade, recur/clinically progress in a subset, but demonstrate a relatively low frequency of histologic progression.

Outcomes and Prognostic Factors in Pediatric Oligodendroglioma: A Population-Based Study

“…Extracortical tumors were associated with the worst prognosis of any region in the CNS in pODG. Rodriguez et al [21] also note the tendency of pODG to develop in extracortical regions rarely associated with adult disease. Peters et al [25] further report 9 of 32 cases analyzed appearing in these extracortical regions and note that such cases were associated with a significantly worse survival.…”

“…This result is supported in the pediatric neuro-oncology literature as well. Creach et al [22] identified 80% of 37 pODG cases as low grade while Rodriguez et al [21] identified 76% of 50 pODG cases as low grade. It is also important to highlight our finding that the improved survival seen in children compared with adults with oligodendroglioma applies only to low-grade tumors.…”

“…A comprehensive review of the literature identified only 7 previous studies that analyzed prognostic factors in pODG [21,22,25,28,29,32,34] , of which only 3 include cases from more than 1 institution [21,25,26] . The largest of these studies by Rodriguez et al [21] reports only 50 cases.…”

“…Age of diagnosis greater than 12 years and tumor location outside of the cerebral cortex have both been linked to poor outcome [22,25,29] . Furthermore, a preponderance of data shows that 1p/19q chromosomal deletion and IDH1 mutation -markers of good prognosis in adults -occur much less frequently in pediatric patients compared to adults [21,23,24,26] , among tumors classified histologically as oligodendroglioma. As mentioned previously though, earlier studies are limited by small population sizes and relatively short length of follow-up, making it difficult to carefully analyze long-term prognostic factors in pODG.…”

“…A comprehensive review of the literature identified 15 studies that investigate the demographics and risk factors of pODG [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] , and only 7 that examine factors related to prognosis [21,22,25,28,29,32,34] . Among these studies, only 3 analyze cases from more than 1 institution [21,25,26] and none includes more than 50 patients. All prior studies identified relied on the 2007 WHO criteria for diagnosis.…”