[1631] Isocitrate Dehydrogenase 1 (IDH1) R132H Mutation Is Not Detected in Angiocentric Glioma.

Aditya Raghunathan, Adriana Olar, Hannes Vogel, John R Parker, Susan C Coventry, Robert Debski, Constance T Albarracin, Kenneth D Aldape, Daniel P Cahill, Suzanne Z Powell, Gregory N Fuller. University of Texas M.D. Anderson Cancer Center, Houston; The Methodist Hospital, Houston, TX; Baylor College of Medicine, Houston, TX; Stanford University School of Medicine, CA; University of Louisville Health Science Center, KY; Kosair Children's Hospital, Louisville, KY

Background: Mutations of isocitrate dehydrogenase-1 gene (IDH1), most commonly replacement of arginine at position 132 by histidine (R132H) have been described in WHO grade II and III diffuse gliomas and secondary glioblastoma, but are rare in primary glioblastoma and other solid tumors. Immunohistochemistry (IHC) utilizing a mouse monoclonal antibody has a high specificity and sensitivity for detecting IDH1 R132H mutant protein in sections from formalin fixed paraffin embedded (FFPE) tissue.
Angiocentric glioma (AG) is a unique neoplasm with mixed features of diffuse gliomas and ependymal differentiation, recently included as a grade I neoplasm in the 2007 WHO classification of CNS tumors. This study was designed to evaluate the presence of the IDH1 R132H in AG.
Design: Three cases of AG were collected and the diagnoses were confirmed. Expression of mutant IDH1 R132H protein was determined by IHC on representative FFPE sections using the anti-Human mouse monoclonal antibody IDH1 R132H (Dianova, Hamburg, Germany). Known cases of grade II-III glioma, confirmed by PCR sequencing, were stained to confirm that mutant IDH1 protein was detected under similar staining conditions.
Results: All three cases were males, 3, 5 and 15 years old, with intra-axial tumors in the right posterior parietal-occipital, right frontal and left frontal lobes, respectively. All three cases showed characteristic morphology of AG, including a monomorphous population of bipolar, slender cells, radially and longitudinally ensheathing cortical blood vessels, as well as diffusely infiltrating parenchyma. All three cases were negative for the presence of IDH1 R132H mutant protein (0/3). All controls showed positive staining of the mutant-specific antibody in grade II-III diffuse gliomas.
Conclusions: IDH1 R132H mutation has been described as a common molecular signature in grade II and III diffuse gliomas, and secondary glioblastomas; however, AG has not been evaluated. The absence of mutant IDH1 R132H protein expression in AG further distinguishes this unique neoplasm from diffuse gliomas.
Category: Neuropathology

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 221, Tuesday Afternoon


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