A Case of Intracranial Solitary Fibrous Tumor Followed by Distant Metastasis without Local Recurrence

Intracranial solitary fibrous tumor is a rare tumor accounting for 0.4% of intracranial tumors, with a high local recurrence rate and a tendency toward metastasis outside the central nervous system. We experienced a case of distant metastasis to the soft tissues and the kidney without local recurrence after gross total resection of the primary intracranial tumor. A 58-year-old male with cognitive impairment and right hemianopsia had a tumor of 5 cm maximum diameter in the left occipitotemporal convexity. Magnetic resonance imaging examinations showed a tumor with a slightly high signal on T1-weighted images, a low signal on T2-weighted images, and uniform and prominent contrast-enhanced images. Intratumoral flow voids were markedly observed. A head computed tomography performed 3 years earlier showed no mass lesions in the same region. Following tumor embolization, a gross total tumor resection was performed. The pathological diagnosis was grade-1 solitary fibrous tumor according to the 2021 World Health Organization central nervous system 5 criteria. A total of 45 Gy of postoperative local radiation therapy was administered. The patient recovered from his cognitive impairment and his right hemianopsia also improved. Although subsequent imaging studies showed no local recurrence, over 8 years after surgery, distant metastases were found in the subcutaneous soft tissue of the medial right femur and the left kidney, all of which were surgically removed. In a literature review, we identified 213 cases of intracranial solitary fibrous tumor having distant metastases with or without local recurrence from 18 reports and found that ours was the ninth case of distant metastasis despite gross total resection without local recurrence.