RARE-22MIXED GLIONEURONAL TUMORS WITH DNET AND RGNT FEATURES: CASE REPORT AND LITERATURE REVIEW

OBJECTIVE: Case report and literature review of mixed glioneuronal tumors with rosette-forming glioneuronal tumor (RGNT) and dysplastic neuroepithelial tumor (DNET) histology. METHODS/RESULTS: A 35 y/o male presented with a third ventricular mass. The mass was sub-totally resected with residual tumor in the thalamus. Pathologic features of a RGNT and DNET were present. The tumor was BRAF V600E wild-type and a PIK3CA mutation (E545K, c.1633G > A) was found. Searching the English literature we found 4 other cases of mixed glioneuronal tumors with RGNT/DNET features; PIK3CA mutations were not assessed in these cases. There are 6 cases of pure RGNTs in the literature with PIK3CA mutations. CONCLUSIONS: A rare sub-set of glioneuronal tumors have mixed RGNT/DNET features. PIK3CA mutations are present in some pure RGNTs, and our case suggests this mutation may be present in cases with mixed DNET/RGNT histology. This finding may have implications for defining tumor biology and pursuing targeted therapy in select cases.