• Mohamed A Elsherif, Doris E Wenger, Rachael A Vaubel, and Robert J Spinner.
• Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, USA.
• World Neurosurg. 2016 Aug 1; 92: 583.e19-583.e24.

BackgroundTenosynovial giant cell tumors are a group of slowly growing benign neoplasms of synovial membrane of joints, tendons, and bursae. The localized type or giant cell tumor of tendon sheath (GCTTS) is the extra-articular form of tenosynovial giant cell tumors. We describe two patients with a GCTTS, confirmed histologically at the time of surgical resection, that was adherent to peripheral nerves. Rare GCTTS can cause extrinsic compression of major nerves.Case DescriptionsThe first patient was a 36-year-old man with a left wrist mass associated with pain and paresthesia in the radial three digits. On ultrasound and magnetic resonance imaging (MRI), the mass appeared arising from the left median nerve with a picture suggestive of an atypical neurogenic tumor; however, the possibility of GCTTS could not be excluded. Intraoperatively, the tumor was adherent to the median nerve without a connection to nearby intercarpal joints. The second patient was a 25-year-old woman with a history of malignant melanoma and an incidentally discovered mass on routine follow-up. MRI of the pelvis showed an ovoid mass related to the right sciatic nerve. The MRI picture was suggestive of a GCTTS, although a benign neurogenic tumor was favored given the anatomic relation to the sciatic nerve. Intraoperatively, the tumor appeared as a nodule implanted on the nerve, and it was easily peeled off.ConclusionWe present a new, rare presentation of GCTTS adherent to peripheral nerves with extrinsic compression. We suggest either an implantation mechanism or an unrecognized extrasynovial origin for such tumors.Copyright © 2016 Elsevier Inc. All rights reserved.

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