Occurrence Of A Solitary Fibrous Tumor Adjacent To The Resection Bed Of A High-Grade Meningioma: A Case Report

Introduction: Solitary Fibrous Tumor (SFT) is a rare aggressive mesenchymal sarcoma derived from aberrantly proliferating blood-vessel pericytes. These neoplasms are typically found in deep soft tissues, however, in rare circumstances, SFT can be found within the central nervous system (CNS). CNS SFT is often confused with meningioma due to similarities on imaging and histology. We present a CNS SFT developing within the resection bed of a previously resected anaplastic meningioma, a diagnosis not previously seen in the literature.Case study: This is the case of a 71-year-old man who, following gross total resection and adjuvant radiation of a WHO Grade III anaplastic meningioma in 2016, presented with recurrence of symptoms in 2020. CT imaging showed recurrence of a mass within the previous resection bed. As part of the diagnostic workup, the patient also underwent CT CAP and was found to have multiple pulmonary and skeletal masses. The patient was scheduled for resection of the CNS neoplasm and a single pulmonary mass with histologic investigation of both. Immunohistochemical staining was utilized, diagnosing both masses as SFT.Conclusions: The aggressive nature of SFT necessitates a timely diagnosis and resection. Given the imaging similarities between meningioma and SFT a high degree of suspicion is needed in the case of clinical presentation abnormal for meningioma. As these neoplasms develop from different precursor cell lines, immunohistochemical interrogation for the NAB2/STAT6 fusion gene is the gold standard diagnostic strategy as it has been shown to be present in 90-100% of SFT and 0% of meningioma. Given the vascular origin of SFT, we hypothesize that aberrant overproduction of VEGF following the initial resection, in the setting of tissue trauma and resultant angiogenesis, resulted in development of this SFT that then subsequently metastasized outside the CNS.