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

This is the authors' abstract. We don't add key points for this paper.

Introduction: Synovial sarcoma (SS) is a rare, aggressive malignancy accounting for approximately 7% of all soft-tissue sarcomas; its occurrence in the peripheral nervous system, particularly the tibial nerve of the distal leg, is exceptionally uncommon. We present a case of primary SS arising from the tibial nerve. To date, only four such cases have been reported in the literature. This case underscores the critical need for prompt, accurate diagnosis in atypical anatomical locations to optimize oncological outcomes and preserve functional extremity. Case Report: A 17-year-old male patient reported first time on date July 09, 2024, with presenting complaints of acute pain in the left calf radiating to sole-foot with palpable mass (3 cm × 1 cm) along the tibial nerve. Initially, it was misdiagnosed as schwannoma by ultrasound, magnetic resonance imaging and in a ultrasonography guided biopsy. However, it was finally diagnosed as monophasic SS of <3 cm in size and intra-compartment, the characteristic SS18-SSX gene fusion. The tumor was classified as Grade 2 (Intermediate) on the basis of Fédération Nationale des Centres de Lutte Center le Cancer. Wide marginal excision of the tibial nerve and scar was done. Complete resection with R0 margins is achieved. From the opposite limb, harvested sural nerve cable grafting was performed. Neurovascular local flap was used to cover. Adjuvant therapy consisted of 32 sessions of post-operative radiation. In accordance with the EORTC 62931 trial ("Adjuvant chemotherapy with doxorubicin, ifosfamide, and lenograstim for resected soft-tissue sarcoma: a multicenter randomised controlled trial"), the absolute overall survival benefit of adjuvant anthracycline and ifosfamide in localized resectable soft-tissue sarcoma is not sufficient to outweigh the substantial risks of treatment-related morbidity, Hence, the adjuvant anthracycline/ifosfamide-based chemotherapy was intentionally skipped (35). At the 2-year and 4-month follow-up, the patient was pain-free, clear of cancer recurrence, with mild sensory blunting in the tibial dermatome, suboptimal motor recovery, resulting in clawing of toes. Musculoskeletal Tumor Society Score is 22/30 which is considered which is considered "Good" Functional Result. Conclusion: This case stresses that all deep-seated soft-tissue masses must be treated with a high index of suspicion for malignancy, regardless of size. A multimodal strategy - combining radical excision, nerve reconstruction, and adjuvant radiotherapy - achieved successful local control and preserved the patient's limb. The heterogeneity of the tumor can pose a diagnostic challenge, even for pathologists specializing in sarcoma.