Synovial Sarcoma of the Tibial Nerve: A Case of Diagnostic Ambiguity and Limb Salvage

A case report published in the Journal of Orthopaedic Case Reports by Varun R Mehta, Rajkumar Mehta, Rahul Parmar, and Sonal R Mehta from Mehta Hospital and V Care Hospital in Gujarat, India, documents a rare synovial sarcoma (SS) arising from the tibial nerve. Only five such cases have ever been reported in medical literature. The authors describe how the tumor was initially misdiagnosed as a benign schwannoma, and how a multimodal surgical approach ultimately achieved limb salvage and more than two years of disease-free follow-up.

The Problem This Research Is Trying to Solve

Synovial sarcoma arising within a peripheral nerve can look nearly identical to a benign schwannoma on imaging. That overlap makes accurate diagnosis difficult and dangerous. Surgery without a confirmed sarcoma diagnosis often results in an excision that is not radical enough, increasing the risk of local recurrence.

The Case

In July 2024, a 17-year-old male presented with shooting pain in his left calf and a tender mass along the tibial nerve. Ultrasound, MRI, and an initial biopsy all suggested schwannoma. A second pathologist found sarcomatous features. Immunohistochemical staining showed positivity for EMA and TLE1, and molecular testing confirmed the SS18-SSX gene fusion. PET-CT staging found no nodal or distant spread. The tumor was classified as Stage IIA, Grade 2, with a Ki-67 index of approximately 20 percent.

The Treatment Approach

The team performed wide-margin excision of the tibial nerve, incorporating the previous biopsy scar, and achieved R0 margins throughout. A sural nerve cable graft from the opposite leg reconstructed the resected nerve, covered by a local neurovascular flap. Adjuvant radiation of 64 Gray in 32 fractions followed. Chemotherapy was omitted based on EORTC 62931 trial evidence. At 28-month follow-up, the patient was pain-free with no recurrence and an MSTS functional score of 22 out of 30, classified as a Good outcome.

Why This Matters

Deep-seated soft-tissue masses must be evaluated with a high index of suspicion for malignancy, regardless of size. A biopsy with full histological and molecular workup, including SS18-SSX testing, should precede any surgery. In this case, a second pathology opinion was what changed the outcome.

Ask for Biomarker Testing: It Opens Doors to Targeted Care

Biomarker testing does not only confirm a synovial sarcoma diagnosis — it determines what treatments you can access. If you or a loved one has synovial sarcoma, ask your care team whether these tests have been completed:

• HLA typing – a blood test checking immune markers required for cell therapies like Tecelra, an FDA-approved personalized therapy using your own immune cells to target cancer.
• MAGE-A4 testing – a tumor test required for Tecelra eligibility and related therapies.
• NY-ESO-1 testing – a tumor test that may qualify you for clinical trials or emerging treatments like lete-cel.

If these have not been ordered, request them now. National labs including Caris Life Sciences and Tempus specialize in sarcoma profiling. For printable resources to share with your care team, visit www.sarcomabiomarkertesting.com.

Source

Mehta VR, Mehta R, Parmar R, Mehta SR. Synovial Sarcoma of the Tibial Nerve in the Distal Leg: A Case of Diagnostic Ambiguity and Multimodal Management Protocol for Limb Salvage and Nerve Reconstruction — A Case Report. J Orthop Case Rep. 2026 Nov;16(11):20–26. DOI: 10.13107/jocr.2026.v16.i11.8374

For more information about the Synovial Sarcoma Foundation, visit synovialsarcoma.org.