Liposarcoma is a malignancy of fat cells that occurs in deep soft tissue and mostly seen in limbs and retroperitoneum. It is the most common mesenchymal tumor of the retroperitoneum. It is detected at very late stages especially when the tumor gains substantial size, weight of several pounds at the time of diagnosis because it is grows very silently in deep tissues in the retroperitoneal area. Therefore, most of the patients with liposarcoma have no symptoms until the tumor is getting very large and pressurizes on neighboring structures which causes tenderness, pain, or functional disturbances. A 61 year-old male patient admitted with one-year history of abdominal pain, distention. Computed tomography demonstrated a large retroperitoneal mass in fat density filling the pelvic cavity extending to epigastric region especially in the left side of abdomen, and displacing intestines to the right and left kidney and pancreas gland posteriorly. At laparotomy the retroperitoneal tumor weighed 13.2 kg, Histologically it was a well-differentiated liposarcoma. Total extirpation surgery is still the most effective treatment in well-differentiated liposarcomas. Close follow-up after surgery is mandotary due to high rates of recurrence (Fig. 3, Ref. 10). Full Text (Free, PDF) www.bmj.sk.