Intracranial Primary Malignant Solitary Fibrous Tumor/Hemangiopericytoma Masquerading as Meningioma: Report of a Rare Case

BACKGROUND: Intracranial solitary fibrous tumors/hemangiopericytomas (SFTs/HPCs) are rare spindle cell tumors originating from interstitial tissue that are usually benign. Primary malignant intracranial SFTs/HPCs are extremely rare. Here we describe a case of malignant intracranial SFT/HPC. CASE PRESENTATION: A 59-year-old woman presented with a space-occupying lesion in the left cerebellar tentorium. Based on imaging findings, we made a preoperative diagnosis of meningioma. During the operation, we found that the tumor had an abnormally rich blood supply and could not be completely removed. Histologic findings, immunophenotype (positive for cluster of differentiation [CD]34, CD99, signal transducer and activator of transcription 6, and B cell lymphoma 2), and a Ki-67 proliferative index of 20–30% for the primary tumor were typical of malignant intracranial SFT/HPC. The tumors showed high sensitivity to radiotherapy and the residual tumor was significantly reduced after intensity-modulated radiation therapy. The patient has had no neurologic symptoms and no recurrence of the tumor in 2 years of follow-up. CONCLUSION: Intracranial SFTs/HPCs are extremely rare. Radiologic examination before the operation is helpful for making a definite diagnosis and judging tumor grade; STAT6 immunohistochemistry is a sensitive alternative diagnostic method. Adjuvant radiotherapy is effective in cases of incomplete resection, and strict follow-up is essential in order to monitor for possible recurrence.