In this episode of SurgOnc Today®, Brian E. Kadera, MD, Ben Hinrichs, MD, and Konstantinos Chouliaras, MD, focus on the diagnosis and work-up of fatty tumors in the extremity and the retroperitoneum. They highlight the imaging features, the utility of biopsy and specifically, MDM2 fluorescence in-situ hybridization. They also review the pitfalls of gross and microscopic margin assessment.