Solitary fibrous tumor of the cerebellopontine angle: A case report with imaging analysis

Solitary fibrous tumors are rare mesenchymal neoplasms of the central nervous system. To date, only approximately 60 patients have been reported. Histological diagnosis is mainly based on immunohistochemical study which shows strong CD34 and vimentin reactivity of the cells. Pre-operative diagnosis remains a challenge to both neurosurgeon and radiologist since most of the imaging findings are thought to be non-specific. In addition, the role of post-operative radiotherapy and the long-term prognosis are both still unclear. Herein, we report a case with a cerebellopontine (C-P) angle solitary fibrous tumor. The imaging characteristics are described in detail. Further analysis and comparison with the imaging findings reported in the literature are also present. The tumor was homogeneous and isodense to brain parenchyma on pre-enhanced CT images and showed intense enhancement after contrast medium administration. In the MR study, the tumor revealed heterogeneous signal intensity on T2-weighted images and strong enhancement on post-contrast images. There were linear or curvilinear hypointensities which were less enhanced in the tumor on both T1- and T2-weighted images. This is a special feature which has been described. Moreover, serial images of dynamic enhancement disclosed a sharp rise of enhancement with a peak at 60 s followed by gradual decline. This pattern is the same as most meningothelial meningioma but different from fibrous meningioma and schwannoma. In addition to the imaging findings, we also noticed the good effect of post-operative radiotherapy for the residual tumor after subtotal resection. The patient was symptom-free with a stable residual tumor in a 2-year follow-up.