INNV-24. METASTATIC HEMANGIOPERICYTOMA TO THE LIVER: DEFINING THE IMPORTANCE OF NAB-STAT2 FUSION

Abstract

Abstract BACKGROUND Meningeal hemangiopericytoma (HPC) is a rare and aggressive vascular tumor which typically occurs in younger adults and has a tendency for local recurrence with delayed metastases outside the CNS. HPC is considered a variant of solitary fibrous tumor (SFT), and is associated with the presence of the fusion oncoprotein NAB2-STAT6. This fusion results in over-expression of the EGR1 gene and results in tumorigenesis. CASE REPORT We present a case of a 49 y/o female with a remote history of left occipital lobe HPC, initially treated with resection and radiotherapy in 2007, who presented with symptoms of right upper quadrant abdominal pain. She was found to have a hypervascular 7 cm mass in the right upper lobe of the liver on magnetic resonance imaging (MRI) studies and subsequently underwent hepatectomy for removal of the mass. Histopathological findings revealed metastatic HPC with features consistent with her primary meningeal tumor that was removed over 13 years agoearlier. Presence of the NAB2-STAT6 fusion was confirmed by targeted genomic analysis. MRI revealed a small focus of nodular enhancement abutting the confluence of the superior sagittal sinus and transverse sinus. This was considered her source of disease and possible dissemination. She was treated with stereotactic radiosurgery to target the lesion. DISCUSSION Given the rarity and often remote medical history of the primary intracranial HPC, this report suggests that 1) long term follow up of HPC is essential and 2) detection of the NAB2-STAT6 fusion can identify and confirm recurrent HPC at metastatic sites. In regards to the latter, distinguishing HPCs from other more benign spindle cell tumors that may mimic SFT (such as fibroblastic meningiomas) is also of therapeutic significance as HPCs typically require adjuvant treatment, (i.e. radiotherapy) as opposed to surgical resection alone.