Supplementary Material for: Multicentric Glioma Develops via a Mutant IDH1-Independent Pathway: Immunohistochemical Study of Multicentric Glioma

<p>Multicentric gliomas are very rare. Due to differences in their tumor types they remain enigmatic.<b> </b>We focused on the pathogenesis of multicentric gliomas and compared their immunoprofile with that of solitary gliomas. This retrospective study included 6 males and 8 females with multicentric glioma (8 glioblastomas, 2 anaplastic astrocytomas, 4 diffuse astrocytomas). Their age ranged from 27 to 75 years and all were treated between 2004 and June 2015. The expression of mutant isocitrate dehydrogenase 1 (IDH1), α-thalassemia X-linked intellectual disability (ATRX), p53, phosphatase and tensin homolog (PTEN), and epidermal growth factor receptor (EGFR) was examined immunohistochemically; for 1p19q analysis we used fluorescence in situ hybridization (FISH). In all patients, immunohistochemical staining was negative for mutant IDH1 and cytoplasmic PTEN; only 1 patient (7.1%) manifested nuclear PTEN positivity. FISH for 1p19q codeletion was negative in all 9 examined samples; 5 of 14 specimens (35.7%) were p53-positive, 9 (64.3%) were EGFR-positive, and 4 (28.6%) were ATRX-negative. The MIB-1 labeling index was 0.9-15.6% for grades II and III, and ranged between 17.3 and 52.4% for glioblastoma. Our results suggest that the pathogenesis of multicentric gliomas is different from the mutant IDH1-R132H pathogenesis of lower-grade glioma and secondary glioblastomas. More studies are needed to confirm the molecular mechanisms underlying the pathogenesis of multicentric glioma.</p>