| Summary: | A 35-year-old man with a history of lumbar surgery and hyperlipidemia presented with a progressively enlarging, palpable, tender mass over the right occipital-parietal calvarium and associated headaches. Initial imaging demonstrated a likely benign calvarial lesion; however, follow-up brain MRI incidentally revealed a second, dural-based midline posterior fossa mass with homogeneous enhancement suggestive of meningioma. The patient underwent resection of the posterior fossa lesion for diagnostic clarification and symptom prevention. The intraoperative frozen section was compatible with a meningioma; however, postoperative permanent pathology ultimately confirmed a cavernous malformation. Three months later, resection of the calvarial mass confirmed a second cavernous malformation. Genetic testing was negative for any known genes associated with familial cavernous malformation. This case highlights the potential for dural-based cavernous malformations, particularly in the posterior fossa, to present with imaging and intraoperative features indistinguishable from meningiomas. Awareness of this mimicry is crucial for accurate preoperative planning and patient counseling when evaluating dural-based lesions in the posterior fossa.
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