Analysis of NAB2-STAT6 Gene Fusion in 17 Cases of Meningeal Solitary Fibrous Tumor/Hemangiopericytoma: Review of the Literature

Solitary fibrous tumor/hemangiopericytoma (SFT/HPC) is a mesenchymal tumor that can affect virtually any region of the body. SFT/HPC of the thoracic cavity and soft tissue has been histologically considered a single biological entity termed SFT; in fact, NAB2-STAT6 gene fusion was recently identified in both diseases. In contrast, meningeal SFT and HPC still need to be investigated in detail with regard to gene fusion variants. The aim of this study was to verify the frequency of NAB2-STAT6 fusion and the relationship between fusion variants and clinicopathologic findings of SFT/HPC, especially meningeal SFT/HPC. We examined the NAB2-STAT6 fusion by reverse transcription polymerase chain reaction with 4 cases of meningeal SFT and 13 cases of meningeal HPC. NAB2-STAT6 fusion transcripts were identified in 12 of 17 cases, including NAB2ex6-STAT6ex17 (4/17, 24%), NAB2ex6-STAT6ex16 and NAB2ex4-STAT6ex2 (3/17, 18%, respectively), and NAB2ex5-STAT6ex16 (2/17, 12%). Three cases showed a pseudopapillary pattern, and 2 of them carried NAB2ex6-STAT6ex17. In addition, our meta-analysis revealed that the major fusion variant in meningeal SFT/HPC was NAB2ex6-STAT6ex16/17 (29/54, 54%), which was also common in soft tissue and intraperitoneum/retroperitoneum but rare in thoracic SFT. Fusion variant significantly correlated with age and histologic diagnosis in meningeal SFT/HPC but not with prognosis. Our results represented that meningeal SFT and HPC were in a single biological spectrum with NAB2-STAT6 gene fusion as was nonmeningeal SFT and further confirmed the organ-specific tumorigenic process and morphologic differences on the basis of fusion variants in meningeal SFT/HPC.