Hybrid peripheral nerve sheath tumor

Case report

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In recent literature, there have been case reports of an extremely rare entity characterized by hybrid peripheral nerve tumors consisting of elements of neurofibroma, schwannoma, and/or perineurioma. The authors present a unique case of a patient with multiple painful hybrid tumors with negative genetic testing for neurofibromatosis Type 1 and no clinical evidence of neurofibromatosis Type 2 or schwannomatosis.

A 28-year-old woman presented with tentatively diagnosed schwannomatosis. She had painful bilateral retromastoid scalp tumors as well as multiple other painful tumors in the distribution of the saphenous, femoral, and sciatic nerves. Her family history was significant for a paternal grandfather with a solitary schwannoma. The patient underwent multiple surgical procedures for tumor resection, including tumors in the regions of the retromastoid scalp, bilateral sciatic nerves, left femoral nerve, and left axilla. These tumors were examined and evaluated histologically. Within the tumors, components of both neurofibromas and schwannomas were found, even though these 2 peripheral nerve sheath tumors have been long considered to be distinct entities. This case report suggests a distinct syndrome that has not previously been appreciated.

Abbreviations used in this paper:EMA = epithelial membrane antigen; NF1 = neurofibromatosis Type 1; NF2 = neurofibromatosis Type 2; PNST = peripheral nerve sheath tumor.

Article Information

Address correspondence to: Shih-Shan Lang, M.D., Department of Neurosurgery, Hospital of the University of Pennsylvania, 3 Silverstein, 3400 Spruce Street, Philadelphia, Pennsylvania 19104. email: shihshan.lang@uphs.upenn.edu.

Please include this information when citing this paper: published online September 14, 2012; DOI: 10.3171/2012.8.JNS111841.

© AANS, except where prohibited by US copyright law.

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Figures

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    a: Coronal STIR sequence through the upper chest and left upper arm demonstrating the presence of high-signal masses involving multiple intercostal nerves and the proximal median nerve. b: Coronal STIR sequence through the pelvis and thighs demonstrating diffuse involvement of bilateral sacral and sciatic nerves by high-signal nerve sheath tumors. c: Axial STIR sequence through the pelvis demonstrating multiple high-signal masses involving the sacral nerves. d: Axial, fat-saturated T1-weighted MRI sequence obtained through the same level as in panel c after the injection of Gd contrast agent. Note patterns of both peripheral enhancement and lack of enhancement of the masses, reflecting relative avascularity of the nonenhancing regions.

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    Photomicrographs. a: Low-power image depicting the classic neurofibromatous morphology comprising spindle cells with abundant intervening collagen bundles in a loose myxoid stroma. b: High-power image depicting tumor cells with dense, eosinophilic collagen bundles resembling shredded carrots. c: Low-power image of a distinct schwannoma tumorlet (arrow), surrounded by neurofibromatous elements. d: Schwannoma tumorlets with classic compact Antoni A morphology comprising densely packed, concentric layers of Schwann cells and adjacent Antoni B areas (arrow). e: Low-power image depicting close association of onion bulb structures with the schwannoma tumorlets. f: High-power image of the onion bulb structures. H & E. Bar = 500 μm (a); 250 μm (c and e); and 100 μm (b, d, and f).

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    Immunohistochemical profile of the hybrid tumors. a–c: S100 staining of the neurofibroma (a), schwannoma tumorlet (b), and onion bulb formations (c). d: EMA staining is confined to the perineurium (arrow). Note the negative EMA staining in the onion bulbs (asterisk). e: CD34 staining highlighting stromal support cells and scattered vasculature. f: Neurofilament stain (NF-TA51) highlighting sparse encompassed axonal processes. g: INI-1 nuclear staining is preserved in the tumor cells, including the schwannoma tumorlets depicted here. Bar = 100 μm.

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