惡性軟組織肉瘤可發生於全身各部位，並常見於四肢、腹膜腔及後腹膜腔。原發中樞神經系統惡性纖維肉瘤為罕見腫瘤，約佔顱內腫瘤的1.5%，此腫瘤被認為源生於腦實質及腦膜之間葉細胞，最常見者包括惡性纖維組織細胞瘤、惡性纖維肉瘤、惡性平滑肌瘤、惡性橫紋肌瘤、惡性血管瘤及未分化瘤。中樞神經系統惡性纖維肉瘤在組織學上常較惡性，並在臨床上有較高復發機率，其易有腦膜及遠端轉移之特性則可與神經膠源腫瘤區分。 中樞神經系統惡性纖維肉瘤較罕見，致使文獻資料及治療經驗均較缺乏；因其易於局部復發及遠端轉移，所以必須以多科整合模式治療。如同四肢及軀幹的軟組織肉瘤，中樞神經系統惡性纖維肉瘤主要治療需仰賴手術切除，但因腦部手術有其限制性，難執行大範圍切除，所以必須給予輔助性放射治療，方可控制殘餘腫瘤細胞。 我們報告一原發中樞神經系統惡性纖維肉瘤案例，其臨床上以右側偏癱及麻痺表現；該病患接受腫瘤全切除術及輔助性放射治療，於追蹤一年期間未有局部復發或遠端轉移。文中另探討中樞神經系統惡性纖維肉瘤之最適切治療方式及預後。

Soft tissue sarcomas can occur in any site throughout the body and are more frequently found in the limbs, peritoneal cavity and retroperitoneum. Primary central nervous system sarcomas are rare and account for only 1.5% of all intracranial tumors. These tumors are thought to arise from mesenchymal elements within the brain parenchyma or its meningeal coverings. Histopathologically, the most common tumor types included malignant fibrous histiocytoma, fibrosarcoma, leimyosarcoma, rhabdomyosarcoma, angiosarcoma and undifferentiated sarcoma. Primary central nervous system fibrosarcomas are usually of high histological grade, with a high rate of recurrence. Their propensity for meningeal and distant relapse distinguishes them from tumors of glial origin. The rare occurrence of primary central nervous system fibrosarcomas leads to a paucity of data in the literature and experience regarding the therapeutic management of these tumors. Because soft tissue sarcomas are aggressive tumors capable of local recurrence and distant metastasis, the need for a multidisciplinary approach is indicated in treating these tumors. As for soft tissue sarcomas of the extremity and trunk, the mainstay of treatment of primary central nervous system sarcomas is surgical excision. While brain surgery must be limited due to the proximity of critical structures, en bloc resections cannot be achieved and adjuvant radiotherapy should be given to control residual disease. We report a case of 30-year-old man who had primary central nervous system fibrosarcoma over left frontal lobe with presentation of progressive right-sided numbness and weakness. The patient was treated with total excision of the tumor followed by adjuvant radiotherapy via cone-down wedged-pair technique. Neither local recurrence nor distant metastasis was identified during a follow-up of 1 year. The optimal treatment and prognosis were discussed.