Intriguing tumor, synovial sarcoma: Hard to diagnose, harder to treat.

Background: Synovial sarcoma (SS) is classified as an aggressive high-grade soft tissue sarcoma that predominantly affects the extremities. Despite its prevalence in the extremities (up to 80%), diagnostic and treatment challenges persist. This study aims to address these challenges by providing a comprehensive analysis of SS in extremities, focusing on diagnostic accuracy and treatment outcomes. The central questions of this study are: What are the diagnostic and treatment challenges associated with SS? How do tumor volume and histologic subtype influence prognosis? What role do immunohistochemistry and genetic markers play in SS diagnosis and management?

Hypothesis: We hypothesize that larger tumor volume and poor histologic differentiation are associated with worse survival outcomes in patients with SS.

Patients and methods: This retrospective study analyzed data from 63 patients diagnosed with SS between 2005 and 2020 at a single center. Patients with complete records of pathology, radiology, and surgery, and a minimum follow-up of 12 months were included. Tumor characteristics, treatment modalities, and follow-up data were reviewed.

Results: The study included 63 patients and 65 tumors. The mean age was 38 ± 17 years. There were 31 females (49%) and 32 males (51%). SS predominantly affected the extremities (n = 63, 97%), especially the lower limbs (n = 49, 75%). Tumor volume, with a mean of 110 ± 176 cm³, was a significant factor, with tumors >30 cm³ associated with higher rates of metastasis (p = 0,006) and reduced survival (p = 0,027). Histologically, 25 (38%) were monophasic, 24 (37%) were biphasic, and 16 (25%) were poorly differentiated, with poorer survival linked to poorly differentiated subtypes. Immunohistochemistry showed high positivity rates for Bcl-2 (89%, 17/19), EMA (88%, 52/59), and TLE1 (87%, 13/15). SS18-SSX fusion gene detected in 73% of cases (8/11). Metastasis occurred in 27 (42%) patients and recurrence in 24 (37%). 15 (23%) patients died from the disease.

Discussion: Accurate diagnosis of SS is crucial for effective management. Clinicians should be aware of negative predictive factors, including tumor volume >30 cm³ and poor histologic differentiation, when making treatment decisions. The study highlights the importance of extended follow-up due to the risk of late recurrence.

Level of evidence: IV.