Modern Pathology



Diagnostic implications of IDH1-R132H and OLIG2 expression patterns in rare and challenging glioblastoma variants

Nancy M Joseph, Joanna Phillips, Sonika Dahiya, Michelle M Felicella, Tarik Tihan, Daniel J Brat and Arie Perry


Figure 2.

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Gliosarcoma. H&E, OLIG2, and IDH1 stained sections from two different examples of gliosarcomas; one example that was negative for R132H IDH1 mutant protein (ac) and one example that was positive for R132H IDH1 (df). Both cases demonstrated a prominent spindle cell component of neoplastic cells arranged in fascicles (a, d). The arrows in (a) and (b) highlight the glial islands that are often seen admixed with the sarcomatous components. These glial regions showed nuclear OLIG2 expression (b) in 93% of cases (Table 1). The sarcomatous component showed patchy/focal OLIG2 positivity in only 14% (e, Table 1) and the remaining 86% of cases were negative for OLIG2 within the sarcomatous areas (b, Table 1). Diffuse staining for R132H IDH1 mutant protein was seen in 7% of gliosarcomas (f, Table 1) and was negative in the remaining 93% of cases (c, Table 1).