Background <p>Surgery at high-volume centers remains the cornerstone of retroperitoneal sarcoma (RPS) treatment, requiring en bloc resection of the tumor with adjacent organs when appropriate.^{<CitationRef AdditionalCitationIDS="CR2 CR3 CR4" CitationID="CR1">1</CitationRef>-<CitationRef CitationID="CR5">5</CitationRef>} This video illustrates a standardized six-stage surgical approach for primary left-sided retroperitoneal liposarcoma, modeled on the same concept of the six-stage technique previously described for right retroperitoneal liposarcoma.^{<CitationRef CitationID="CR6">6</CitationRef>}</p> Patient and Methods <p>A 73-year-old man presented with a 13-cm primary left retroperitoneal high-grade dedifferentiated liposarcoma. The tumor displaced the descending colon and abutted the pancreatic tail and psoas muscle. Following Tumor-Board evaluation, the patient received preoperative chemotherapy (three cycles of epirubicin–ifosfamide), resulting in disease stability upon restaging.</p> Results <p>The patient underwent en bloc resection of the left retroperitoneal mass, including the ipsilateral kidney, adrenal gland, and colon. A healthy plane was identified between the tumor and the pancreatic tail. Given the patient’s age, prior chemotherapy, and high-risk of pancreatic fistula, the distal pancreas and spleen were dissected free and preserved. On the posterior side, the psoas muscle was tightly adherent to the tumor and was resected to ensure oncological adequacy. This structured medial-to-lateral approach allows early vascular control and safe identification of critical structures.</p> Conclusions <p>Resecting a left RPS is a complex procedure that demands a diverse set of surgical skills. This six-stage approach, developed over two decades in a high-volume center, provides a reproducible and oncologically sound benchmark, applicable virtually in all cases while ensuring a resection adherent to the principles of surgical oncology.</p>