PATH-45. Rare but Real: A Case Series of Metastatic Meningioma with Systemic Involvement

Abstract Meningiomas are typically benign, slow-growing tumors originating from the arachnoid cells. Most meningiomas stay in the cranial or spinal regions, but less than 1% metastasize outside the Central Nervous System (CNS), mainly Grade 2/3 cases, spreading to the lungs, liver, and pleura. Data is limited due to rarity. Therefore, we present a case series from our institution. We conducted a retrospective review of 1,545 brain cancer patients from our database from 2012-2024, 96 of whom had pathology confirmed meningiomas. Six of them developed extracranial metastatic meningiomas. Clinical data, including imaging, biopsy results, and surgical outcomes, were reviewed, focusing on genomic details, histopathology, disease progression, and treatment. Among the six patients with metastatic meningiomas, two had Grade 2 atypical meningiomas, and four had Grade 3 anaplastic meningiomas. Metastases occurred to the scalp and orbit (1 case), parotid gland (1 case), vertebra (3 cases), liver (1 case), lungs (1 case), and neck (1 case). Imaging (CT, MRI, PET-CT) and follow-up biopsies confirmed meningioma origin of metastases except in one patient. These patients received multiple surgical resections, chemotherapy, targeted therapy (everolimus, Ixazomib, and tazemetostat), and localized radiation. Mutations in MTAP, BRACA-1 associated protein-1, CDKN2A/B, and H3K27me3 were noted during the molecular analysis. Despite aggressive treatment, three patients experienced disease progression and died, while the others showed partial response to therapy. Survival averaged 110 months from diagnosis, dropping to 26 months post-metastasis despite aggressive treatment. Extra CNS metastatic meningiomas, while rare, pose significant diagnostic and therapeutic challenges. High-grade meningiomas are more likely to metastasize; early detection of metastatic spread is challenging. Our findings highlight the need for close follow-up and vigilance for distant metastasis, especially in recurrent or high-grade meningiomas with distinct mutations.