Metastatic High-Grade Serous Ovarian Carcinoma Presenting as a Temporal Lobe Glioblastoma Mimic: A Diagnostic Pitfall

High-grade serous ovarian carcinoma (HGSOC) is the most common subtype of ovarian cancer, known for its aggressive nature and unique pattern of metastasis. Brain metastases from ovarian carcinoma are uncommon, with HGSOC rarely presenting with multifocal lesions that radiographically mimic the multi-centric growth pattern of a primary glioblastoma, particularly following a prolonged period of clinical remission, leading to diagnostic ambiguity. We report the case of a 69-year-old woman with a prior history of HGSOC who presented with new-onset cognitive and language deficits. Neuroimaging indicated a prominent temporal lobe mass radiologically suggestive of glioblastoma. Histopathological examination and immunohistochemistry demonstrated features consistent with metastatic HGSOC, showing strong paired box gene 8 (PAX8) positivity and absence of glial markers. This case highlights the importance of considering a range of differential diagnoses for intracranial lesions in patients with a history of malignancy by using a multidisciplinary approach to interpret clinical, radiologic, and histopathologic data, while emphasizing the crucial role of immunohistochemistry in distinguishing metastatic disease from primary brain tumors.