RETROPERITONEAL SYNOVIAL SARCOMA A DIAGNOSTIC CHALLENGE: AN UNCOMMON CASE

Abstract

Introduction: Synovial sarcomas are rare and aggressive soft-tissue tumors, typically arising in the extremities. Primary retroperitoneal synovial sarcomas represent <1% of retroperitoneal sarcomas and are extremely uncommon. Their diagnosis is challenging due to their deep anatomical location and nonspecific clinical presentation. Case Presentation: A 49-year-old man with a history of classic seminoma with an atypical component treated in 2009 presented with progressive left lumbar pain and intermittent paresthesias. Imaging showed an infrarenal para-aortic mass displacing the duodenum and aorta, infiltrating the psoas, contacting the vertebral foramen, and associated with a pathological L3 fracture. Biopsy and immunohistochemistry confirmed monophasic synovial sarcoma. Interventions: The patient received neoadjuvant chemotherapy (MAI) and image-guided radiotherapy. Surgical treatment included en-bloc retroperitoneal tumor resection, L3 corpectomy, and spinal reconstruction in a two-stage approach, in collaboration with neurosurgery. Results: Postoperative imaging demonstrated adequate spinal reconstruction with no complications. The patient presented no neurological deficits and reported improvement in preoperative paresthesias. At the time of writing, there was no evidence of local or distant recurrence. Conclusions: Primary retroperitoneal synovial sarcoma is exceptionally rare and poses significant diagnostic and therapeutic challenges due to its proximity to vital structures. Multidisciplinary evaluation and careful surgical planning are essential for optimal oncologic outcomes. This is the first documented case in Colombia and in Latin America of primary retroperitoneal synovial sarcoma with spinal involvement. MeSH Keywords: Synovial Sarcoma; Retroperitoneal Neoplasms; Lumbar Vertebrae; Corpectomy; Neoadjuvant Therapy; Spinal Fusion.