Vascular synovial sarcoma masquerading as deep vein thrombosis: a diagnostic pitfall-a case report

Background: Intravascular synovial sarcoma is a rare disease with only 14 cases documented globally to date. To the best of our knowledge, we present the 15th case, highlighting the diagnostic challenge, rapidly progressive course of this malignancy and the need for greater clinical awareness. Case Presentation: A female patient in her early 20s presented with a painful swelling in the right inguinal region and right lower limb oedema, initially considered to be DVT. Imaging revealed a mass involving the right external iliac and common femoral veins. She underwent surgical excision of the mass, and histopathological evaluation confirmed intravascular biphasic synovial sarcoma, supported by molecular diagnostic testing. Patient received postoperative chemotherapy. However, there was local recurrence of the disease within 5 months of completing chemotherapy and within a year of surgical resection. Conclusions: This case emphasizes that not all cases presenting as DVT may be benign, especially in young patients without apparent risk factors. Underlying malignancies, including sarcomas, should be considered in the differential diagnosis. Advanced imaging techniques are critical for early detection and surgical planning. Early multidisciplinary involvement is essential for optimizing outcomes. Given the rarity and aggressive nature of this disease, further research is needed to guide standardized treatment strategies and improve survival.