Fig. 2

Examination of an oligodendroglioma case with differential methylation diagnosis. Patient SU-156 developed two local recurrences in the frontal lobe as shown by MRI scans. The primary tumor was subclassified as oligodendroglioma, IDH-mutant and 1p/19q-codeleted by DNA methylation profiling, whereas the tumor recurrences were assigned to the novel oligosarcoma, IDH-mutant subclass. The primary tumor showed typical oligodendroglioma morphology by hematoxylin and eosin (H&E) stains whereas the recurrent tumors had sacromatous components. Nuclear positivity of ATRX was detected in all the three tumor samples. Copy number alteration profiles, retrieved from the methylation array data, indicated hyperdiploidy in the tumor recurrences. Scale bars: 100 µm