Solitary fibrous tumor of the posterior fossa: a rare and atypical case report.

INTRODUCTION

Solitary fibrous tumor (SFT) is an uncommon mesenchymal neoplasm of fibroblastic origin. Intracranial SFTs account for less than 1% of primary central nervous system tumors, and posterior fossa location is exceptional. Although often slow-growing and histologically bland, intracranial SFTs have an intermediate biological potential due to delayed recurrence and extracranial metastases. We report a posterior fossa SFT mimicking a common extra-axial lesion.

CASE PRESENTATION: A 60-year-old woman presented with a 1-year history of progressive headaches, vomiting, and right-sided weakness. Examination revealed right hemiparesis, cerebellar dysfunction, and central facial palsy. MRI showed a large right posterior fossa extra-axial mass compressing the fourth ventricle and causing obstructive hydrocephalus. She underwent a posterior suboccipital craniectomy with gross total resection. Histology showed patternless spindle-cell proliferation with staghorn vessels and collagenous stroma. Immunohistochemistry was positive for CD34, STAT6, and vimentin and negative for EMA, S-100, and GFAP, confirming SFT. Postoperatively, she developed hydrocephalus requiring ventriculoperitoneal shunting (Clavien-Dindo grade IIIb). At 3 months, her neurological status improved, and MRI showed no recurrence.

DISCUSSION: This case highlights the diagnostic difficulty of a posterior fossa SFT, which may mimic a meningioma or other extra-axial tumors. Atypical features included a rare infratentorial location, obstructive hydrocephalus, and postoperative cerebrospinal fluid diversion despite complete resection. STAT6 immunostaining remains central, especially where molecular testing is unavailable.

CONCLUSION

Posterior fossa SFT is rare, characterized by benign-appearing histology yet unpredictable behavior. Complete resection, immunohistochemical confirmation, hydrocephalus management, and long-term radiological surveillance are essential.