Glioblastoma : Epithelioid type

Epithelioid subtype of glioblastoma consists of tumor cells with abundant eosinophilic cytoplasm, vesicular nuclei with prominent nucleoli, and distinct cytoplasmic borders. The cells are arranged in cohesive patternless sheets. It resembles metastatic carcinoma or melanoma which must be ruled out. This specimen is from a 26 y/o female who presented with headaches and hearing loss of sudden onset. MRI scan showed a mass in the left temporal lobe. The tumor cells were strongly positive for GFAP, weakly positive for CAM5.2 and negative for melanoma markers. Necrosis, increased mitotic activity, and endothelial proliferation were also noted in this tumor. Epithelioid glioblastomas have been shown to harbor BRAF V600E mutations in up to 50% of cases and these patients may benefit from targeted therapy with vemurafenib (Ref: Am J Surg Pathol 2015;39:528-540)