OLIG2 and glioma: All glial tumors were high grade based on the revised diagnosticclassification of canine gliomas.34 In a recent prognostic study on canine glial tumors, the histologic featuresof high-grade gliomas correlated with poor survival.43 Previous case reports in cattle also described high-grade glialtumors.31,33,64 One tumor classified as of oligodendroglial origin based on themucinous matrix, absence of GFAP labeling, OLIG2 labeling of more than 90% ofneoplastic cells, and typical cell phenotype in most areas contained osteoidmetaplasia.