Pathology: hybrid nerve sheath tumours

Hybrid schwannoma/perineurioma

• Circumscribed; variably cellular; spindle cells with storiform-fascicular pattern

• Eosinophilic cytoplasm with long tapering processes

• Ovoid nuclei with occasional pleomorphism; inconspicuous mitotic activity

• Collagenous-myxoid stroma

• IHC: S100, SOX10

• RNA-seq: CHD7::VGLL3 gene fusion

Hybrid schwannoma/perineurioma

• Circumscribed 

• Spindle cell neoplasm with fascicular-storiform pattern

• Pale eosinophilic cytoplasm

• Round-ovoid nuclei with mild atypia and scattered hyperchromasia and pseudonuclear inclusions; inconspicuous mitotic activity

• Variable collagenous-myxoid stroma and delicate vasculature

• IHC: S100, SOX10, CD34, claudin-1, GLUT-1, glial fibrillary acid protein

• RNA-seq: CHD7::VGLL3 gene fusion

• PMID: 19623031, 33649458 

Hybrid schwannoma/perineurioma

• Circumscribed 

• Spindle-stellate cells with loose fascicular pattern

• Eosinophilic cytoplasm with tapering bipolar processes

• Monomorphic ovoid nuclei; inconspicuous mitotic activity

• IHC: S100, SOX10

• RNA-seq: CHD9::VGLL3 gene fusion

• PMID: 19623031, 33649458 

Hybrid schwannoma/perineurioma

• Circumscribed 

• Spindle cell neoplasm with loose fascicular pattern

• Eosinophilic cytoplasm with tapering bipolar processes

• Ovoid hyperchromatic nuclei with mild atypia and occasional pseudonuclear inclusions; inconspicuous mitotic activity

• IHC: S100, SOX10

• RNA-seq: CHD9::VGLL3 gene fusion

• PMID: 19623031, 33649458 

Hybrid schwannoma/perineurioma*

• Spindle cell neoplasm with fascicular-storiform pattern

• Pale eosinophilic cytoplasm

• Ovoid, occasionally elongated, nuclei with minimal atypia; inconspicuous mitotic activity

• Variable collagenous stroma and delicate vasculature

• RNA-seq: GAB1::ABL1 gene fusion

* Despite morphologic and immunohistochemical overlap with hybrid schwannoma/perineurioma, it is conceivable this may ultimately represent a distinct entity (PMID: 34036664)