Orbital hybrid schwannoma/perineurioma: A case presentation

Hybrid Schwannoma-Perineurioma of the Orbit

“…3,10,16 No patients had evidence of tumor recurrence and none of the orbital HPNSTs were malignant or underwent malignant transformation. 1,3,7,10,[14][15][16][17] Our patient shares similar characteristics with previously reported orbital HPNSTs, including proptosis; a well-circumscribed, heterogeneously enhancing orbital mass; no recurrence after resection; and no malignant transformation of the tumor. However, our case is unusual in that the majority of orbital HPNSTs described thus far were of the neurofibroma-schwannoma subtype, while schwannoma-perineurioma was previously reported in 1 patient only.…”

“…8,9 Hybrid neurofibroma-schwannoma is the second most common HPNST subtype outside of the orbit that is strongly associated with neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2)-related schwannomatosis. 1,7,[10][11][12] Neurofibroma-schwannoma features neurofibroma comprising a mixed population of fibroblasts, Schwann cells, and perineurial cells in a collagenous and occasionally myxoid background and cellular nodules composed of monomorphic Schwann cells in a palisaded Antoni A arrangement with Verocay body formation. 2,4,12,13 Hybrid neurofibroma-perineurioma, the least frequent HPNST subtype, has been described in association with NF1.…”

“…3 HPNSTs are extremely rare in the orbit, with 8 cases reported in the literature: 6 cases describe neurofibroma-schwannoma, 1 case describes a neurofibroma-perineurioma, and 1 case describes a schwannoma-perineurioma. 1,3,7,10,[14][15][16][17] The paucity of cases of HPNSTs in this region may be an underestimate, reflecting a lack of awareness of this relatively recently recognized entity. Four previously reported patients were male and 4 were female, with an average age of 52 years (median 52.5, range 31-78).…”

“…14 Three patients had a visual loss on initial presentation; 2 patients experienced diplopia. 1,3,15 Imaging typically revealed a heterogenous appearing mass in the orbit. Six out of 8 HPNSTs caused the displacement of orbit structures with 4 compressing the optic nerve, 1 compressing the supraorbital nerve, and 2 displacing the rectus muscles.…”

“…H PNST is a rare benign neoplasm typically presenting as a painless mass in the subcutaneous tissue or dermis. 1 HPNST demonstrates a biphasic pattern containing mixed components of neurofibroma, schwannoma, and perineurioma with either a clear transition between cell types or an intermingling of cell types. 2 Several subtypes of HPNST have been identified, including neurofibroma-schwannoma, schwannoma-perineurioma, and neurofibroma-perineurioma.…”