Rhabdoid meningioma, light micrograph. Meningioma is the most common primary intracranial tumour in adults. Most meningiomas are WHO Grade I and behave in a benign fashion. The remaining 20% are WHO Grade II or III with atypical to anaplastic (malignant) features and an aggressive clinical course. Rhabdoid meningiomas are Grade III tumours according to the WHO classification. They are composed of rhabdoid cells that classically present with eccentric nuclei, prominent eosinophilic cytoplasmic inclusions of intermediate filaments and a discohesive arrangement. The presence of rhabdoid morphology is synonymous with aggressive behaviour with a recurrence risk of 87%, and a 13% risk of extracranial metastases.