Prognostic significance of NAB2-STAT6 fusion variants and TERT promotor mutations in solitary fibrous tumors/hemangiopericytomas of the CNS: not (yet) clear

International audience; Grading of meningeal solitary fibrous tumors/hemangiopericytomas(SFTs/HPCs) of the central nervous system (CNS)is nowadays based on histologic criteria as described in therevised fourth edition of the WHO Classification of CNStumors [10] or the more recently published, updated versionof the Marseille Grading System (MGS) [11]. Histologybasedgrading of CNS SFTs/HPCs allows for discriminatingsubgroups with significant differences in prognosis. However,the often-piecemealresection of these tumors mayhamper adequate evaluation of mitotic activity and necrosis,and thereby assessment of malignancy grade. NAB2–STAT6fusion is the molecular hallmark of both soft tissue SFTs andCNS SFTs/HPCs, and the resultingfusion protein accumulatesin the nucleus and acts as a transcriptional activatorof early growth response mediated pathways with STAT6immunohistochemistry being a very sensitive and specifictool for their diagnosis [5, 8, 12, 14]. For soft tissue SFTs,particular NAB2–STAT6 fusion variants as well as telomerasereverse transcriptase (TERT) promoter mutations leadingto telomerase activity and tumor cell immortalization havebeen reported to have prognostic value. Some studies haveincluded CNS SFTs/HPCs in their cohort, but because ofsmall numbers and lack of (long term) follow-up data theprognostic value of these markers for CNS SFTs/HPCs isstill unclear.