Supplementary Material for: Diagnostic and Therapeutic Challenges of Rare Concurrent Intracranial Meningioma and Oligodendroglioma

Introduction
Concurrent primary brain tumors are rare clinical entities, with a prevalence ranging from 0.1% to 0.5% of all diagnosed brain tumors. The co-occurrence of meningioma and oligodendroglioma is particularly uncommon, posing unique diagnostic and therapeutic challenges. We describe the case of a patient diagnosed with concurrent meningioma and oligodendroglioma and review the existing literature on this rare phenomenon.

Case presentation
A 55-year-old female patient with a history of seizures presented to the emergency department with worsening headaches, nausea, and vomiting. She had a known right frontoparietal intracranial mass but had previously declined surgery. Magnetic resonance imaging revealed extensive fluid-attenuated inversion recovery (FLAIR)/T2 hyperintensity around the lesion, which had slowly increased over 5 years; the growth of the lesion was producing mass effect with significant midline shift. The patient underwent urgent hemicraniectomy with subsequent resection. Clinical evaluation, imaging studies, and histopathological examination were conducted to confirm the diagnosis. Genetic and molecular analyses were also performed to explore potential underlying mechanisms. Histopathological findings confirmed a diagnosis of an isocitrate dehydrogenase–mutated World Health Organization Grade II oligodendroglioma with 1p/19q codeletion, along with a Grade I meningioma.

Conclusion
The coexistence of meningioma and oligodendroglioma represents a rare clinical event. Surgical management remains the cornerstone of treatment. Further investigation into the genetic and environmental factors that contribute to the co-occurrence of such tumors could pave the way for more targeted therapeutic strategies.