Clinical Profile, Pathology, and Molecular Typing of Gliomas with Oligodendroglial Morphology: A Single Institutional Experience.

Background: Diffuse gliomas are represented in the 2007 WHO classification of CNS tumors as astrocytomas, oligoastrocytoma, and oligodendroglioma of grades II/III and glioblastomas WHO grade IV, which was a pure morphologic classification. WHO 2016 classification combines morphology with molecular markers like IDH, ATRX, and 1p/19q codeletion to give an integrated diagnosis.

Methods: The study was carried out on formalin fixed paraffin embedded tissues from 54 patients including three pediatric patients. Molecular studies were performed to know the 1p/19q codeletion status, IDH1R132H, and ATRX immunoexpression. Also, the IDH1R132H status was correlated with survival data.

Results: The study included 54 tumors with oligodendroglial morphology. IDH1R132H positivity was seen in 85% of total cases and codeletion was seen in 72%. The integrated diagnosis revised the cases into oligodendroglioma (39), astrocytoma (5), and glioblastoma (6).IDH mutant tumors were found to have better survival than negative ones which was statistically significant.

Conclusion: This study emphasizes the need for molecular work up of tumors with oligodendroglial morphology with readily available techniques like IHC and Fluorescence in situ hybridization.