Turkish Neurosurgery
Molecular Subgrouping Based on Immunohistochemistry in Medulloblastoma: a Single-Center Experience
Berrin Babaoglu1, Sahin Hanalioglu2, Ali Varan3, Kader Karlı Oguz4, Burcak Bilginer2, Anıl Dolgun5, Figen Soylemezoglu1
1Hacettepe University, Pathology, Ankara,
2Hacettepe University, Neurosurgery, Ankara,
3Hacettepe University, Pediatric Oncology, Ankara,
4Hacettepe University, Radiology, Ankara,
5Hacettepe University, Biostatics, Ankara,
DOI: 10.5137/1019-5149.JTN.45863-23.2

Aim:Medulloblastomas (MBs) are the most commonly observed malignant brain tumors affecting children; they can be classified into molecular subgroups based on the 2016 and 2021 WHO classifications, as WNT-activated, SHH-activated and TP53-wild type, SHH-activated and TP53-mutant, and non-WNT/non-SHH. However, the molecular methods to determine these subgroups are not easily accessible for routine testing as they are expensive. Here, we investigated the efficacy of immunohistochemical methods to determine molecular subgroups and prognostic predictions of MB.Material and Methods:β-catenin, GAB1, YAP1, filamin A and p53 were immunohistochemically stained, and MYC and MYCN fluorescent in situ hybridization (FISH) procedures were applied to 218 cases in our series.Results:Based on the histomorphological characteristics of the cases, 67.9% were deemed classic MB; 15.6% as desmoplastic/nodular medulloblastoma (DNMB); 12.8% as large cell/anaplastic (LC/A) MB; 3.7% as medulloblastoma with extensive nodularity (MBEN). Molecular characteristics revealed that 50.5% had non-WNT/non-SHH; 33.9% had SHH-activated and TP53-wildtype; 8.7% had WNT-activated; 6.9% had SHH-activated and TP53-mutant. According to the survival curves, LC/A MBs or non-WNT/non-SHH tumors showed the worst prognosis, whereas DNMBs and WNT-activated tumors showed the best prognosis. Classic MBs or SHH-activated tumors showed a moderate course. MYCN amplification was found to act as an independent poor prognostic factor in the study.Conclusion:The distribution of histological subtypes and molecular subgroups, amplification rates, and prognostic data obtained through immunohistochemical methods in our study were consistent with those reported in the literature. It was therefore hypothesized that the determination of molecular subgroups by immunohistochemical methods can be useful in daily diagnostic practice, especially in centers with limited access to molecular techniques.

Corresponding author : Berrin Babaoglu