IMG-126. Bony Metastatic Extra-Axial Invasion of Primary Glioblastoma: A Case Series and Review of the Literature

Glioblastoma is the most common primary malignant CNS neoplasm. It typically presents as an intra-axial lesion with central necrosis, heterogeneous enhancement with surrounding edema. Glioblastomas can very rarely be found extra-axial or extra-cranially with even more rare cases of distant metastasis, however this is typically seen with progression of disease in the postoperative setting. Primary presentation of glioblastoma with extra-axial invasion is an uncommon occurrence. The underlying etiology of extra-axial glioblastoma is largely unknown. Here, we present two different retrospective cases of extra-axial IDH wildtype glioblastoma on first clinical presentation, prior to any surgical intervention. Bony invasion of the skull was present in both cases. Pathological diagnosis was confirmed through immunohistochemistry and molecular analysis. In one case MGMT promoter methylation was present, but absent in the other patient. One patient died 4 months postoperatively. Although cases of gliosarcoma invading the bone are known and well reported, primary glioblastoma with bony invasion is not common. We performed a literature review using Pubmed and identified only 12 cases of glioblastomas with bony erosion of the cranium on initial presentation. Unique genetic mutations may be associated with increased propensity for extra-axial invasion. Glioblastoma is a highly malignant and invasive CNS neoplasm however, extra-axial invasion is an atypical presentation. Further analysis of these tumors may identify more aggressive features and mutations that may cause atypical invasion and hence affect surgical considerations and further treatment.