10076- MPC-8 MOLECULAR DIAGNOSIS OF MEDULLOBLASTOMA: CHARACTERISTICS OF JAPANESE CASES AND DIAGNOSTIC METHODS FOR WNT MBS.

Abstract BACKGROUND Medulloblastomas have been subdivided into pathological morphological groups, but since 2012, consensus has been reached on four different molecular subgroups, including wingless (WNT)-activated, sonic hedgehog (SHH)-activated, groups 3 and 4, which have been included in the WHO classification since 2016 and have been to date, the era has seen a greater emphasis on molecular genetic diagnosis. Although DNA methylation arrays are used as the Golden Standard in many developed countries, in many Asian countries, including Japan, and in clinical practice in developing countries, the diagnosis of the name and type of disease is often based on pathological findings and immunostaining. WNT MB is known as a group with a particularly good prognosis if treated appropriately, and the reliable diagnosis (salvage) of WNT MB patients without omissions is extremely important for future clinical trials. However, no consensus has yet been reached on the optimal method for correct and leak-free diagnosis. METHODS JPMNG: 267 cases registered since 2012 at 43 facilities in Japan participating in the Japanese Pediatric Molecular Neuro-oncology group (244 cases were analyzed in the final analysis). Molecular genetic diagnosis was performed using Nano string, DNA sequencing, DNA methylation array, etc., to classify the patients into four types. RESULTS The four typing groups were WNT: 39 (16%), SHH: 61 (25%), Group3: 42 (17%) and Group4: 102 (41.8%) cases, respectively. Of these, all cases were positive for (1) CTNNB1 in 39 of 39 cases (100%) and (2) monosomy6 in 35 of 35 cases (100%), especially in the diagnosis of WNT. CONCLUSIONS The molecular genetic features of WNT MB were analyzed from 244 cases of medulloblastoma accumulated at the JPMNG. The diagnosis of WNT MB can be made more conveniently and accurately by utilizing multiple modality approaches, in addition to the use of DNA methylation arrays.