High-Grade Glioma With Parotid Metastasis: A Case Report of Long-Term Treatment and Follow-Up.

High-grade gliomas (WHO Grade 4) are aggressive and common primary brain tumors of glial origin with poor prognosis. The classification of high-grade astrocytomas has evolved, improving the distinction between tumor subtypes. Previously, isocitrate dehydrogenase (IDH)-mutant astrocytomas that progressed to Grade 4 were referred to as secondary glioblastomas. They are now categorized as astrocytoma, IDH-mutant, WHO Grade 4, reflecting their unique molecular and clinical features. While intracranial spread is common in high-grade gliomas, extracranial metastases remain exceptionally uncommon. This case report highlights a 31-year-old woman who initially presented with seizures and progressive neurological symptoms. Initial imaging revealed a diffuse astrocytoma (WHO Grade 2), confirmed by histopathology and molecular testing as an IDH mutant. Despite surgery, radiotherapy, and chemotherapy, follow-up imaging demonstrated progression to high-grade glioma (WHO Grade 4) with intracranial tumor growth and, eventually, extracranial metastases to the cervical lymph nodes and parotid gland. Histopathological examination of the metastatic lesions revealed high proliferative activity and molecular studies confirmed specific genetic alterations consistent with the primary tumor. This case underscores the importance of comprehensive clinical evaluation, vigilant imaging follow-up, and advanced molecular diagnostics in high-grade gliomas (WHO Grade 4). It also highlights the rare metastatic behavior of IDH-mutant astrocytomas (previously classified as secondary glioblastomas) and emphasizes the need for long-term monitoring and individualized treatment strategies to improve outcomes.