Purely cystic meningioma: extremely rare clinical and radiographic mimic of intra-axial glioblastoma multiforme with systematic review of the literature. Illustrative case

Purely cystic meningiomas are extremely rare extra-axial neoplasms that can mimic aggressive malignancies, like glioblastoma multiforme (GBM), because radiologically and intraoperatively they lack a visible solid component and demonstrate postcontrast enhancement and significant vasogenic edema. The authors present a case of a purely cystic intra-axial meningioma mimicking GBM with an accompanying systematic review of the literature. An 84-year-old female presented with expressive dysphasia. MRI revealed a 3-cm inhomogeneously enhancing intra-axial left temporal lobe mass with apparent MRI presentation of central necrosis, suggesting a high-grade glioma. Intraoperatively, the lesion appeared vascular and infiltrative like a GBM; however, histopathological and immunohistochemical analyses (somatostatin receptor 2 antigen positive, progesterone receptor positive, glial fibrillary acidic protein negative) confirmed an angiomatous meningioma (WHO grade 1). Postoperatively, the patient’s symptoms resolved, and 10 years of annual follow-up MRI studies confirmed no recurrence. Only 3 other purely cystic meningioma cases (extra-axial) were identified in the literature. Cystic meningiomas are rarely GBM “imitators.” Surgeons should consider cystic meningioma when classic radiological hallmarks are absent. Despite an aggressive imaging profile, these tumors are biologically and clinically benign. Gross-total resection remains the gold-standard treatment, offering excellent long-term prognosis and the potential for a permanent cure. This case highlights the need for histological tissue diagnosis before final treatment plans are considered. https://thejns.org/doi/10.3171/CASE26438