Retroperitoneal sarcoma resection is a surgical procedure performed to remove a malignant (cancerous) tumor, known as retroperitoneal sarcoma, located in the retroperitoneal space. The retroperitoneal space is the area behind the peritoneum, or the lining of the abdomen, which contains organs such as the kidneys, pancreas, and parts of the gastrointestinal tract. The goal of this surgery is to remove the entire tumor and any surrounding tissue that may be affected to prevent the spread of cancer.