Synovial Sarcoma
Synovial sarcoma is a high-grade malignant soft tissue tumor primarily affecting the extremities of young adults. Diagnosis requires MRI, histopathology, and molecular confirmation of the SS18–SSX fusion gene. Treatment is multidisciplinary, centered on complete surgical excision with limb preservation when feasible, combined with perioperative radiotherapy and chemotherapy for large, deep, or high-risk lesions. Prognosis depends on tumor size, depth, margin status, and recurrence, with lung metastasis being the most common pattern of spread. Long-term surveillance is essential due to the potential for late metastatic relapse.
Epidemiology
Synovial sarcoma is a high-grade soft tissue sarcoma predominantly affecting adolescents and young adults, most commonly arising in the extremities, especially the lower limbs. The median age at diagnosis is in the 30s, with a slight male predominance. Diagnostic delays are common, with up to 35% of cases initially undergoing unplanned excision before referral to specialized centers (Broida 2024). The lungs are the most frequent site of metastasis (≈70%), followed by bone (10–20%) and lymph nodes (17%) (Wu 2017).
Diagnosis & Imaging
Diagnosis relies on a combination of MRI, histopathology, and molecular testing. Core needle biopsy with immunohistochemistry and fusion testing (SS18–SSX) should be performed at a sarcoma center before any surgery.
MRI is the modality of choice for local staging (size, depth, neurovascular or bony involvement).
Triple sign (mixed high, intermediate, low signal on T2) is a typical imaging feature.
Chest CT is essential for staging due to pulmonary metastasis risk.
PET-CT can help assess treatment response or recurrence.
Pathology
Histologically, synovial sarcoma presents as monophasic, biphasic, or poorly differentiated forms, the latter associated with worse prognosis.
Immunoprofile: Bcl-2, EMA, and TLE1 are commonly positive (Li 2024).
Molecular confirmation via SS18–SSX gene fusion testing is diagnostic, particularly when morphology or IHC is inconclusive (Amary 2007).
Treatment Overview
Optimal management requires multimodal therapy within a specialized multidisciplinary team.
Surgery: Complete (R0) resection with limb preservation is the cornerstone of treatment. Limb salvage is feasible in >60% of cases, and negative margin status strongly predicts local control and survival (Sharma 2024).
Radiotherapy: Indicated for residual disease or high recurrence risk. Preoperative RT (≈50 Gy) followed by R0/R1 resection improves local control (Gingrich 2020). Surgery is typically scheduled 3–4 weeks post-RT.
Chemotherapy: Neoadjuvant anthracycline–ifosfamide regimens are used for large, deep, or borderline-resectable tumors. Adjuvant chemotherapy is considered for high-risk patients and systemic disease.
Prognosis
Prognosis depends on tumor size, depth, margin status, bone invasion, mitotic count, and recurrence. Adverse factors include tumor >5 cm, deep location, positive margins, axial site, and local relapse (Song 2017, Broida 2024). Late metastases (>5 years) are not uncommon; therefore, long-term surveillance is essential. Early re-excision with negative margins and appropriate perioperative therapy significantly improves metastasis-free and disease-specific survival.
References
Broida SE, Arguello AM, Sullivan MH, et al. Unplanned Excision of Synovial Sarcoma: Factors Associated with Recurrence and Survival. Cancers (Basel). 2024;16(18):3157. doi:10.3390/cancers16183157
Wu Y, Bi W, Han G, Jia J, Xu M. Influence of Neoadjuvant Chemotherapy on Prognosis of Patients with Synovial Sarcoma. World J Surg Oncol. 2017;15(1):101. doi:10.1186/s12957-017-1165-9
Li C, Krasniqi F, Donners R, et al. Synovial Sarcoma: The Misdiagnosed Sarcoma. EFORT Open Rev. 2024;9(3):190–201. doi:10.1530/EOR-23-0193
Amary MF, Berisha F, Bernardi Fdel C, et al. Detection of SS18–SSX Fusion Transcripts in Formalin-Fixed Paraffin-Embedded Neoplasms: Analysis of Conventional RT-PCR, qRT-PCR, and FISH as Diagnostic Tools. Mod Pathol. 2007;20(4):482–496. doi:10.1038/modpathol.3800761
Sharma J, Deo SVS, Kumar S, et al. Clinicopathological Profile and Survival Outcomes in Patients with Localised Extremity Synovial Sarcomas. Clin Oncol (R Coll Radiol). 2024;36(4):e97–e104. doi:10.1016/j.clon.2024.01.018
Gingrich AA, Marrufo AS, Liu Y, et al. Radiotherapy is Associated With Improved Survival in Patients With Synovial Sarcoma Undergoing Surgery: A National Cancer Database Analysis. J Surg Res. 2020;255:378–387. doi:10.1016/j.jss.2020.05.075
Song S, Park J, Kim HJ, et al. Effects of Adjuvant Radiotherapy in Patients With Synovial Sarcoma. Am J Clin Oncol. 2017;40(3):306–311. doi:10.1097/COC.0000000000000148
