Metastatic Skull Base Tumor From Thymic Carcinoma Mimicking Tolosa-Hunt Syndrome

A 39-year-old male without contributory medical history had sustained progressive double vision, ptosis, and trigeminal pain for 2 weeks. Physical examination revealed total ophthalmoplegia and visual field defect with normal blood examination and chest radiography. Cranial computed tomography revealed a hyperdense mass in the left frontotemporal fossae with bony erosion. Magnetic resonance imaging confirmed a broad-based, intensely enhanced extraaxial tumor of 4×4×4 cm diameter with dural tail sign. Cerebral angiography demonstrated insignificant blood supply both from the internal carotid and middle meningeal arteries. Nearly total tumor resection was achieved via orbitofrontotemporal craniotomy. Intraoperative findings revealed the extraaxial tumor with broad attachment to the dura mater and invasion to the optic and oculomotor nerves. Histological examination revealed hypercellular tumor with significant cell atypism, mitotic activity, and focal necrosis. Immunohistochemical staining was positive for AE1/3 and c-kit, but negative for glial fibrillary acidic protein. Systemic examination performed postoperatively revealed a thymic tumor without additional remote lesions. The final diagnosis was metastatic brain tumor from thymic carcinoma. Rapid progression of neurological impairment inconsistent with a benign extraaxial tumor needs prompt surgical intervention.