The Site of Origin of Medulloblastoma: Surgical Observations Correlated to Molecular Groups

SIMPLE SUMMARY: Medulloblastoma is one of the most common malignant brain tumor types and comprises the molecular groups WNT-MB, SHH-MB TP53-wildtype, SHH-MB TP53-mutant and non-WNT/non-SHH MB. Developmental gene expression data suggest that these molecular groups arise from different sites of origin in the developing brain. Therefore, we hypothesized that intraoperative observation could enable the neurosurgeon to predict the molecular group during surgery and opt for a less aggressive resection in molecular groups with favorable prognosis to preserve neurological function. We reviewed the intraoperative reports, surgical videos and information on the molecular group of 58 patients who were operated at our institution from 1996 to 2020. Our data demonstrate that the correct prediction of the molecular group based on the intraoperatively observed site of origin was limited. Based on our results, we conclude that maximal safe resection should remain the aim of surgery irrespective of the observed site of origin. ABSTRACT: Developmental gene expression data from medulloblastoma (MB) suggest that WNT-MB originates from the region of the embryonic lower rhombic lip (LRL), whereas SHH-MB and non-WNT/non-SHH MB arise from cerebellar precursor matrix regions. This study aimed to analyze detailed intraoperative data with regard to the site of origin (STO) and compare these findings with the hypothesized regions of origin associated with the molecular group. A review of the institutional database identified 58 out of 72 pediatric patients who were operated for an MB at our department between 1996 and 2020 that had a detailed operative report and a surgical video as well as clinical and genetic classification data available for analysis. The STO was assessed based on intraoperative findings. Using the intraoperatively defined STO, “correct” prediction of molecular groups was feasible in 20% of WNT-MB, 60% of SHH-MB and 71% of non-WNT/non-SHH MB. The positive predictive values of the neurosurgical inspection to detect the molecular group were 0.21 (95% CI 0.08–0.48) for WNT-MB, 0.86 (95% CI 0.49–0.97) for SHH-MB and 0.73 (95% CI 0.57–0.85) for non-WNT/non-SHH MB. The present study demonstrated a limited predictive value of the intraoperatively observed STO for the prediction of the molecular group of MB.