Adjunctive markers for classification and diagnosis of central nervous system tumors: Results of a multi-center neuropathological survey in Korea

Background: The revised 4th 2016 World Health Organization (WHO) classification of tumors of the central nervous system (CNS) classification has adopted integrated diagnosis encompassing the histology and molecular features of CNS tumors. We aimed to investigate the immunohistochemistry, molecular testing, and testing methods for diagnosis of CNS tumors in pathological labs of tertiary centers in Korea, and evaluate the adequacy of tests for proper diagnosis in daily practice. Methods: A survey, composed of eight questions concerning molecular testing for diagnosis of CNS tumors, was sent to 10 neuropathologists working in tertiary centers in Korea. Results: For diagnosis of astrocytic and oligodendroglial tumors, all 10 centers performed isocitrate dehydrogenase mutations testing and 1p/19q loss of heterozygosity. For glioneuronal tumors, immunohistochemistry (IHC) assays for synaptophysin (n=9), CD34 (n=7), BRAF(VE1) (n=5) were used. For embryonal tumors, particularly in medulloblastoma, four respondents used IHC panel (growth factor receptor bound protein 2-associated protein 1, filamin A, and yes-associated protein 1) for molecular subclassification. Regarding meningioma, all respondents performed Ki-67 IHC and five performed telomerase reverse transcriptase promoter mutation. Conclusions: Most tertiary centers made proper diagnosis in line with 2016 WHO classification. As classification of CNS tumors has evolved to be more complex and more ancillary tests are required, these should be performed considering the effect of necessity and justification.