Rectal carcinoid tumor metastasis to a skull base meningioma.

Carcinoid tumors are rare, slow-growing neuroendocrine tumors that most frequently develop in the gastrointestinal tract or lungs and have high potential for metastasis. Metastasis to the brain is rare, but to another intracranial tumor is extremely rare. Of the intracranial tumors, meningiomas are the most common to host metastases, which may be related to its rich vascularity and E-cadherin expression. We describe the case of a 65-year-old female with active chemotherapy-treated neuroendocrine carcinoma who presented with left-sided facial numbness, headaches, and blurry vision. Initial imaging revealed a 1 cm irregular dural-based left petrous apex mass suggestive of a meningioma that was re-imaged four months later as a rapidly enlarging, extra-axial, mass extending into the cavernous sinus, effacing Meckel's cave that resembled a trigeminal schwannoma. Pathology revealed a carcinoid tumor metastatic to meningioma. While the mass displayed characteristic imaging findings of a schwannoma, rapid growth in the setting of known active malignancy should prompt the clinician to consider mixed pathology from metastatic disease or a more aggressive meningioma.