Case Report: Rare presentations of glioblastoma: three multifocal and one cerebellar cases highlighting the value of shared clinical experience.

Background: Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults, typically presenting as a single supratentorial lesion. Multifocal/multicentric, and infratentorial variants are rare but clinically significant, often mimicking metastatic disease and limiting the feasibility of standard treatment. Their management remains challenging, and dedicated therapeutic guidelines are lacking. Methods: We describe four uncommon GBM presentations, three multifocal supratentorial tumors and one cerebellar tumor, and integrate their clinical trajectories with a review of the literature to highlight diagnostic and therapeutic considerations. Results: Across cases, diagnosis required comprehensive neuroimaging and, in several instances, exclusion of an extracranial primary malignancy. Molecular profiles were consistent with Conclusion: Rare presentations of GBM, including multifocal and cerebellar disease, carry substantial diagnostic ambiguity, limited therapeutic options, and a markedly poor prognosis. Early multidisciplinary evaluation, optimized supportive care, and research focused on tailored treatment strategies are urgently needed to improve outcomes in these challenging GBM subtypes.