Retroperitoneal soft tissue sarcoma, a rare mimic and important differential of iliopsoas abscess

This case report highlights the diagnostic challenges posed by retroperitoneal soft tissue sarcoma (STS) presenting as an iliopsoas abscess, mimicking common symptoms and radiological findings. This patients’ symptoms recurred despite multiple percutaneous drains and revisions over a period of months. Further investigation revealed a partly solid, partly cystic mass consistent with sarcoma. Surgical excision confirmed the diagnosis, but recurrence necessitated palliation. This case emphasizes the importance of differential diagnoses of iliopsoas collection and the need for research into alternative imaging modalities to aid clinicians and radiologists in differentiating benign retroperitoneal collections from malignancy.