Microsatellite Instability in Glioblastoma: Is It Really Relevant in Tumor Prognosis?

AIM: To evaluate the frequency and prognostic significance of microsatellite instability (MSI) in patients with glioblastoma (GBM immunohistochemical analysis of mismatch repair (MMR) proteins was performed. MATERIAL and METHODS: A total of 71 patients with GBM who underwent surgery between 2011 and 2019, were included in the study. MMR protein expression was examined using immunohistochemistical analysis of tumor tissue samples; the association between the MMR status and clinicopathological findings was evaluated. RESULTS: Immunohistochemical analysis revealed expressions of MLH1, MSH2, MSH6, and PMS2 proteins in 67 (94.4%), 65 (91.5%), 67 (94.4%), and 64 (90.1%) patients, respectively. Among the 71 patients, 64 (90.1%) expressing all MMR proteins were considered microsatellite stable (MSS), and 7 (9.9%) patients showing loss of at least one of the MMR proteins were considered to show MSI. Tumor recurrence was noted in 25 (39.1%) patients in the MSS GBM group, and 4 (57.1%) patients in the MSI GBM group (p=0.433). The overall median survival was 30.65 +/- 5.1 and 10.71 +/- 5.2 months in the MSS GBM and MSI GBM groups, respectively (p=0.059). CONCLUSION: The results of this study showed no significant relationships between MMR protein expression and recurrence rates or overall survival in patients with GBM.