The finding that meningeal solitary fibrous tumors (SFTs) and meningeal hemangiopericytomas (HPCs) are both characterized by NAB2-STAT6 gene fusion has pushed their inclusion in the WHO 2016 Classification of tumors of the central nervous system (CNS) as different manifestations of the same entity.
The 2016 central nervous system (CNS) World Health Organisation (WHO) Update has merged the entities of meningeal solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) into a single entity based on the presence of the nerve growth factor 1A (NGFI-A) binding protein 2 (NAB2)- signal transducer and activator of transcription 6 (STAT6) gene fusion in these tumors.
Most notable classification changes include: adding 'hybrid nerve sheath tumours' to the spectrum of benign nerve sheath tumours; an updated definition of atypical meningioma (WHO grade II), including cases with brain invasion; recognizing dural solitary fibrous tumour (SFT) and haemangiopericytoma (HPC) as a single tumour entity characterized by NAB2 and STAT6 gene fusions for which the term SFT/HPC was chosen; recognizing that pituitary granular cell tumour, spindle cell oncocytoma, and pituicytoma all share nuclear expression of TTF-1, possibly representing a spectrum of a single nosological entity derived from posterior pituitary glial cells.
NAB2-STAT6 gene fusion is a molecular characteristic of solitary fibrous tumors (SFT) and hemangiopericytoma, underscoring their definition as one diagnostic entity.
Clinicopathological data, including yearly follow-ups, are required for meningeal SFTs/HPCs to define the correlation of variants of NAB2-STAT6 fusion gene.
We present two cases of meningeal solitary fibrous tumor (SFT)/hemangiopericytoma (HPC) with immunohistochemistry of STAT6 and analysis of NAB2-STAT6 fusion genes.
Solitary fibrous tumors/hemangiopericytomas with different variants of the NAB2-STAT6 gene fusion are characterized by specific histomorphology and distinct clinicopathological features.