Retroperitoneal synovial sarcoma a diagnostic challenge: an uncommon case

Synovial sarcoma (SS) is a rare and aggressive mesenchymal neoplasm that can arise at various anatomical sites. However, it typically occurs in the soft tissues of the extremities, particularly the lower limbs [1]. This tumor makes up 0.8%-10% of soft tissue sarcomas and about 1% of reported retroperitoneal tumors. [2,3,4]. Its highest incidence is observed in young adults, with no clear differences by sex. Because of its low frequency, epidemiological data are primarily derived from isolated reports and small series. [2,3,4,5]. Although its name suggests a synovial origin, the tumor does not develop from the synovial membrane; the term is kept because of morphological similarities to embryonic synovium [6,7]. Its diagnosis is difficult, not only because it can resemble benign lesions, but also because of morphological overlap with other sarcomas. When it occurs in the retroperitoneum, its detection is often delayed because this anatomical space allows for progressive tumor growth without specific symptoms. Retroperitoneal lesions can resemble other aggressive neoplasms; this complicates differential diagnosis and leads to significant treatment delays, which negatively affect prognosis. In this context, most retroperitoneal cases are detected at advanced stages and are linked to lower survival rates, estimated at 20%-29% at five years [4, 6].Retroperitoneal SS is extremely rare, with fewer than 35 cases documented in the literature [4,5]. Spinal involvement is exceptional, and most reports lack or have limited follow-up [2]. Due to the absence of standardized guidelines for retroperitoneal SS—the National Comprehensive Cancer Network (NCCN), the European Society for Medical Oncology (ESMO), and the American Society of Clinical Oncology (ASCO) include this tumor within the general management of soft tissue sarcomas—its approach, diagnosis, and treatment pose a challenge for surgeons [1,2].