Anaplastic oligodendroglioma arising from the brain stem and featuring 1p/19q co-deletion

Synchronous supratentorial and infratentorial oligodendrogliomas with incongruous IDH1 mutations, a case report

Infratentorial oligodendrogliomas, a rare pathological entity, are generally considered metastatic lesions from supratentorial primary tumors. Here, we report the case of a 23-year-old man presenting with a histopathologically confirmed right precentral gyrus grade 2 oligodendroglioma and a concurrent pontine grade 3 oligodendroglioma. The pontine lesion was biopsied approximately a year after the biopsy of the precentral lesion due to disease progression despite 4 cycles of procarbazine-CCNU-vincristine (PCV) chemotherapy and stable supratentorial disease. Histology and genetic analysis of the pontine biopsy were consistent with grade 3 oligodendroglioma, and comparison of the two lesions demonstrated common 1p/19q co-deletions and TERT promoter mutations but distinct IDH1 mutations, with a non-canonical IDH1 R132G mutation identified in the infratentorial lesion and a R132H mutation identified in the cortical lesion. Initiation of Temozolomide led to complete response of the supratentorial lesion and durable disease control, while Temozolomide with subsequent radiation therapy of 54 Gy in 30 fractions resulted in partial response of the pontine lesion. This case report supports possible distinct molecular pathogenesis in supratentorial and infratentorial oligodendrogliomas and raises questions about the role of different IDH1 mutant isoforms in explaining treatment resistance to different chemotherapy regimens. Importantly, this case suggests that biopsies of all radiographic lesions, when feasible and safe, should be considered in order to adequately guide management in multicentric oligodendrogliomas.

Adult brainstem gliomas: Correlation of clinical and molecular features

BACKGROUND

Brainstem gliomas are rare in adults and overall have superior survival outcomes compared to pediatric brainstem gliomas.

PATIENTS AND METHODS

We conducted a retrospective data and tissue analysis of all adult patients (≥ 18 years old) with World Health Organization (WHO) Grade II, III, and IV brainstem gliomas in the University of Texas MD Anderson Cancer Center institutional database from 1990 to 2012.

RESULTS

We identified 143 cases in adults ages 18 and over. There were 28 glioblastomas, 43 anaplastic astrocytomas, 15 diffuse astrocytomas, and 11 gliomas not otherwise specified, and in 46 cases the diagnosis was made radiographically. 128 (89.5%) cases were classified radiographically as diffuse and of the focal tumors, 9 of the 15 were WHO Grade III or IV tumors. Increasing tumor grade and contrast enhancement were associated with significantly reduced overall survival. The median overall survival for the entire cohort was 32.1 months similar to previously published studies. Two of 25 grade II and III tumors, and 1 of 17 glioblastomas had IDH1 mutations on immunohistochemical testing. Nine cases had sufficient tissue for mutation profiling, 1 case had a BRAF V600E mutation and 2 had 2 PIK3CA mutations.

CONCLUSIONS

Survival outcomes for adult WHO Grade II to IV brainstem gliomas were similar to supratentorial IDH1 wild-type tumors of similar grade and histology. Potentially actionable mutations can be identified from small biopsy samples in a subset of adult brainstem gliomas.

Clinicopathologic features of pediatric oligodendrogliomas: a series of 50 patients

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 7 mo 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.