De-differentiation associated with drop metastasis of a recurrent intracranial solitary fibrous tumor: a case report and literature review

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.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.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.