PATH-23. HIGHLY INFILTRATING OLIGODENDROGLIOMAS SHOW DIFFERENT MORPHOLOGY FROM TYPICAL OLIGODENDROGLIOMAS WHILE MAINTAINING GOOD RESPONSE TO CHEMO-RADIATION THERAPY

Abstract Oligodendrogliomas are diffuse gliomas located in the cerebral hemisphere, and MRI typically show swollen cortex subcortical white matter by tumor cells. IDH mutation 1p/19q co-deletion define oligodendrogliomas WHO classification, these genetic alterations associated with good response to chemo-radiation therapy better prognosis compared IDH-mutant astrocytomas. We reviewed findings of 60 co-deleted tumors which were diagnosed at Dokkyo Medical University since 1999. Of those, 3 cases showed highly infiltrating pattern more predominant than infiltration involved multiple lobes. retrospectively investigated those for histological features, treatment, clinical outcome. There 2 males 1 female. faint-brushed Gd enhancement around center tumor-infiltrated area case, while there was no enhancing lesion other cases. All three underwent stereotactic biopsy. Histologically, all lacked typical oligodendroglioma morphology: cells have irregular round, oval elongated nuclei without perinuclear halo had dense, closed chromatin similar astrocytoma. Two chemotherapy (TMZ PAV accordingly), radiation case as primary treatment. Interestingly, responded well not only treatments but also administered after recurrence, although eventually succumbed tumor. PFS 16, 37, 67 months OS 104, 70, 115 each, worse end apparently Highly appeared significantly different features from that primarily involve cortex. The underlying mechanism such differences might specific and/or gene expression may affect treatment response.