Case Report: Intramedullary solitary fibrous tumor at the C7-T1 level diagnosed by STAT6 and treated with maximal safe resection.

Intramedullary solitary fibrous tumor is an exceptionally rare spindle-cell neoplasm of the central nervous system and is rarely diagnosed before surgery because the clinical presentation and imaging findings are non-specific. We report a man in his early 60s with more than 7 years of progressive bilateral lower-extremity numbness that worsened during the month before admission without an identifiable precipitating event. Magnetic resonance imaging demonstrated an enhancing intramedullary lesion at the C7-T1 level. The patient underwent microscopic tumor resection through a posterior C7-T2 laminectomy under intraoperative ultrasound guidance and multimodal intraoperative neurophysiological monitoring, including somatosensory evoked potentials, transcranial motor evoked potentials, D-wave monitoring, and free-running electromyography. Gross total resection was achieved without new neurological deficit. Histology showed spindle cells in fascicular and storiform arrangements with branching staghorn-like vessels. Immunohistochemistry demonstrated nuclear STAT6 positivity with co-expression of CD34, CD99, and Bcl-2. Mitotic activity was low, with only 2-3 mitoses per 10 high-power fields, and no definite tumor necrosis was identified, supporting the diagnosis of a CNS WHO grade 1 solitary fibrous tumor. Sensory symptoms improved after surgery, and no recurrence was detected on magnetic resonance imaging at 18-month follow-up. This short-term outcome is encouraging, but long-term radiological surveillance remains necessary.