GFAP, Ki67 and IDH1: perhaps the golden triad of glioma immunohistochemistry

Excerpt

In this issue of Acta Neuropathologica, Capper et al. [2] describe a monoclonal antibody that specifically and sensitively recognizes the IDH1 (isocitrate dehydrogenase 1) protein carrying the R132H mutation in routinely processed (formalin-fixed, paraffin-embedded) tissues. In 2008, hotspot sequence mutations at position 132 of IDH1 were discovered in 12% of glioblastomas [4] and in about 70% of diffuse astrocytomas, oligodendrogliomas, oligoastrocytomas and secondary glioblastomas [1], a finding that has been confirmed by several other studies. Because more than 90% of IDH1 mutations are of the R132H type and mutations are assumed to be present in all tumor cells, this antibody is able to identify virtually all glioma cells in paraffin sections from the majority of grade-II diffuse gliomas and from their more malignant descendants. When compared with a PCR- and restriction endonuclease-based assay for different IDH1 mutations recently described by the same group of authors [3], the immunohistochemical technique is easier to perform and is presumably more sensitive, whereas R132H-immunonegative cases will require additional PCR or sequencing analysis to search for other types of IDH1 and IDH2 mutations. Although the antibody still needs to be evaluated by other institutions on a large number of specimens, it may represent one of the seminal achievements in diagnostic neuropathology of the past decades. …