Expression of IDH1, ATRX, p53 in Diagnosis of Gliomas as Per 2016 WHO Classification

Abstract

Introduction: The 2016 World Health Organisation (WHO) classification of tumours of the Central Nervous System (WHO CNS 2016 classification) is used to classify diffuse gliomas as astrocytoma, Oligodendroglioma (ODG), glioblastoma which are three prognostically distinct groups based on Isocitrate Dehydrogenase (IDH1), alpha thalassaemia/mental retardation, x-linked (ATRX) mutations, p53 and 1p/19q co-deletion status. Although WHO CNS 2022 classification has been brought in use, it is based on molecular studies. In a resource limited setting like in many Indian diagnostic centres it’s difficult to apply the WHO CNS 2022 classification. It is felt that WHO CNS 2016 classification has not lost its utility. Aim: To investigate the Immunohistochemistry (IHC) status of IDH1, ATRX, p53 in diagnosis of diffuse glial tumours and to classify them according to WHO 2016. Materials and Methods: This cross-sectional study was conducted at Bharati Vidyapeeth Medical College, Hospital and Research Centre, Pune, Maharashtra, India for two years and six months (July 2020 to December 2022). Thirty-two diffuse glioma cases and IHC markers IDH1, ATRX, p53 were evaluated. Ki-67 index was additionally done. Results: Total 32 cases were studied, 19 cases were male. Mean age of the patients was 40.13 years. Fourteen patients belonged to WHO Grade-II, 6 to Grade-III, and 12 to GradeIV. As per the IHC findings and histopathological features, there were 16 (50%) patients with diffuse astrocytoma, while 12 (37.5%) and 4 (12.5%) patients were diagnosed as glioblastoma and ODG respectively. Reclassification of these cases was done depending on IHC results where IDH1 was positive in 71.9% cases, ATRX was positive in 40.6% cases and p53 was positive in 15.6% cases. This result includes all the cases where these IHC markers showed reactivity. The diagnosis of four patients was modified based on findings of IHC markers. Conclusion: The study demonstrates subgrouping of gliomas based on IDH1, ATRX, p53. There was no significant association between grade of tumour and Ki-67 expression.