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Solitary fibrous tumors (SFTs) and haemangiopericytomas (HPCs) are rare mesenchymal tumors in central nervous system (CNS). Although progressed recognition to the diagnosis and treatment of SFT/HPCs, it still remains many confusions regarding on its occurrence, aggressive evolution, malignant transformation, dedifferentiation phenomenon, distant metastasis and unpredictable propensity. Seventeen cases of CNS SFT/HPCs who underwent surgical treatment from January 2010 to December 2020 were collected in the authors' institute. Clinical, radiological, pathological data and followup details were reviewed in all cases. The age of this series was 41-73 years old. Seven cases located subtentorially, five cases originated from middle skull base and four in supratentorial. MRI shows iso-signal intensity on T1WI, and heterogeneous slightly long/short signal on T2WI. There is significant contrast after gadolinium-enhancement. It is easy to be misdiagnosed before surgery. The positive rate of nuclear STAT6 is 94.12%, higher than CD34 (87.5%). Eight patients were grade I, eight grade II and one in grade III. Five cases developed tumor relapse, in which two cases had local intracranial recurrence combined with dissemination and metastasis of cerebrospinal fluid in the spinal canal, accompanied by pathological malignant transformation, and another one occurred blood metastasis. CNS SFT/HPCs are rare intracranial tumors with unpredictable propensity. Gross total resection is critical to its overall clinical prognosis. Given its potential recurrence and malignant transition, adjuvant radiotherapies are recommended when necessary, and long-term follow-up is indispensable. The underlying molecular biological mechanisms are still needed to be further exploration. [ABSTRACT FROM AUTHOR]

Background: Central nervous system is a rare occurring location of solitary fibrous tumors (SFTs). SFTs have a potential for recurrence, which is the leading cause of death in patients with these disease entities. De-differentiation phenomenon combined with cerebrospinal fluid (CSF) dissemination through drop metastasis of STFs from intracranial to intraspinal has only been reported in extremely limited cases., Case Description: Herein, we present a case of SFT in a 54-year old male. MRI showed characteristic of mixed high and low signal with 6.3 cm × 6.5 cm × 5.9 cm. After radical surgical resection, the pathology indicated benign SFT. However, MRI re-examination of 22 months later detected local recurrence, concomitant with spreading of intracranial and intraspinal through CSF dissemination. And interestingly, the second pathology found de-differentiation phenomenon and malignance of SFT, in which some areas transformed to rhabdomyosarcoma., Conclusion: This is the first case report of recurrent intracranial SFT de-differentiating to rhabdomyosarcoma concurrent with CSF pathway drop metastasis. Benign intracranial SFTs have the potential of de-differentiation, which may play an important role in its distant metastasis. The underlying molecular biological and pathological mechanisms of benign SFT malignance transformation still warrant further exploration.