Epithelioid glioblastoma mimicking metastatic brain tumor: A case report and literature review.

Epithelioid glioblastoma (eGBM) is a rare subtype of glioblastoma, generally associated with a poorer prognosis than conventional GBM despite maximum resection and standard chemoradiotherapy. Here, we report a case of a 78-year-old man who presented with left hemiplegia and a well-circumscribed right frontal lobe lesion on imaging, initially suspected to be a metastatic brain tumor. Surgical resection revealed a firm, clearly demarcated mass. Histopathological examination showed features consistent with eGBM, including epithelioid and rhabdoid cells, necrosis, and high proliferative activity (Ki-67 index: 41%). Immunohistochemistry indicated IDH-wildtype GBM with negative BRAF V600E. Despite postoperative radiotherapy and temozolomide chemotherapy, the tumor recurred, and the patient died 1 year and 10 months after surgery. Even if a tumor appears well-circumscribed with minimal edema, a diagnosis of eGBM should be considered to avoid treatment delays if no primary lesion is detected. Following a diagnosis of eGBM, prognosis remains variable; therefore, careful pathological evaluation, including immunohistochemistry and molecular analysis, is essential to guide treatment decisions.