PATH-58. REAPPRAISAL OF HISTOLOGICAL FEATURES AND MOLECULAR ANALYSIS OF LOWER GRADE GLIOMAS AND ASSOCIATION WITH OVERALL SURVIVALS

INTRODUCTION Based on WHO 2016 classification of grade II and III glioma (lower grade glioma/LrGG), the pathological diagnosis of oligodendroglioma is associated with IDH mutation status and 1p/19q codeletion. It was reported that the classical oligodendroglioma features closely related to the presence of 1p/19q codeletion. In this study, we compared histology of oligodendroglial features with molecular prognostic factors such as ATRX, TERT, IDH1/2 and copy number aberrations and their relations with patients’ prognoses. METHODS In this study, we analyzed 94 cases of primary LrGG resected in 1990 to 2016 in Keio University Hospital, Japan. Using WHO 2007 classification of LrGG, we re-diagnosed the tumors based on their histological features and compared them to their initial diagnoses (made by the pathologists on the time of resections). The presence of classic for oligodendroglioma (CFO) features were closely documented. ATRX mutation was analyzed by immunohistochemistry. IDH1/2 and TERT mutation status were analyzed using Sanger sequence. Copy number aberrations analyzed using comparative genomic hybridization (CGH). In addition, we analyzed IDH-mut/codeleted tumors with cancer genetic panel. RESULTS Re-diagnosis shown there is a shift of trend toward oligodendroglioma diagnoses from astrocytoma and a trend of change from grade II to grade III. IDH-mut/codel tumors shown no correlation between CFO and molecular prognostic factors nor CNAs but there was correlation between overall survival and molecular factors such as CIC (p= 0.046) and FUBP1(p= 0.03). IDH-mut/non-codel tumors shown no correlation between CFO and overall survival but ATRX and gain of 8q were found to be correlated with pathological diagnosis. CONCLUSION There is a lot of change in histological diagnosis of oligodendroglioma from each eras. IDH-mut/codel tumors shown there is correlation between FUBP1 and CIC with overall survivals. IDH-mut/noncodel tumors shown there is correlation between gain of 8q with overall survivals.