soft tissue sarcomas are very rare tumors ; however , there are many histologic subtypes . among those subtypes , furthermore , among sarcomas originating within the retroperitoneum , which constitute 1015% of all soft tissue sarcomas , liposarcomas are the most common histologic type , accounting for 41% of these tumors [ 2 , 3 ] . liposarcomas are generally located in the head , neck , trunk , mediastinum , upper and lower extremities , gastrointestinal tract , and retroperitoneum . they commonly occur in patients aged 4060 years , and men and women are equally affected . the dimensions and weight of liposarcomas are variable ; those over 20 kg are called herein , we report a giant retroperitoneal liposarcoma weighing 25.0 kg , encasing the entire left kidney and adherent to adjacent structures which was successfully removed with kidney and aorta preserving . the patient had not experienced any symptoms , such as abdominal pain , nausea , vomiting , constipation , dyspepsia , or dyspnea . the patient was admitted to the hospital and underwent contrast - enhanced computed tomography ( ct ) of the abdomen . the scan revealed a huge fatty mass originating from the retroperitoneum probably indicative of retroperitoneal liposarcoma . the spleen was pushed anteriorly and the small bowel was deviated to the right side of the intra - abdominal space by the mass ( fig .  1 ) . because the patient was old , we decided to attempt organ - preserving surgery for the removal of the tumor to minimize the morbidity . adherence of the mass to the diaphragm , stomach , spleen , pancreas , and aorta could be observed . the greatest difficulty was that the tumor was encasing the entire left kidney and adherent to the aorta . although the entire left kidney was encased with the huge tumor , neither the renal parenchyma nor the ureter was invaded . we successfully performed a salvage of the left kidney by wide excision and separated the tumor from the aorta by shaving it away , thus preserving both kidney and the aorta . the specimen measured 45.0  30.0  11.0 cm and weighted 25.0 kg ( fig .  2 ) . microscopic examination showed a combined type of liposarcoma ( tumor component : well - differentiated liposarcoma , more than 95% , myxoid liposarcoma , less than 5% ) . an average of 12 mitotic figures were noted per high - power field . according to the grading system of the french federation of cancer centers sarcoma group , she underwent regular follow - up examinations for 16 months after the operation . at 16 months , a follow - up ct scan revealed a newly defined low - density soft tissue mass in the aortocaval and preaortocaval area , measuring 3.5  1.8  4.3 cm , suggesting a locally recurrent tumor in the retroperitoneum . we performed positron emission tomography ( pet ) , which revealed tumor recurrence in the retroperitoneum . fluorescence in situ hybridization showed mdm2 amplification , which was consistent with a diagnosis of well - differentiated liposarcoma . after the second surgery , the patient underwent regular follow - up ct scans for approximately 12 months , and to date , there has been no evidence of tumor recurrence liposarcoma is one of the most common soft tissue sarcomas , constituting approximately 20% of cancers within that group . between 10 and 15% of soft tissue sarcomas originate within the retroperitoneal space , and the most common type among these is liposarcoma . however , liposarcoma is very rare overall , accounting for 0.20.3% of all malignancies . multiple factors , such as site and depth of origin , margin involvement after resection , and histologic grade affect survival rates for patients with liposarcoma . if the size of the tumor is less than 2.5 cm , the rate of metastasis at 5 years is approximately 3% . on the other hand , the rate of metastasis at 5 years is between 55 and 60% in cases of tumors larger than 20 cm . this is because the retroperitoneal space allows the tumor to grow to a large size before the appearance of clinical signs and symptoms . therefore , the tumor is often diagnosed at the advanced stage . resection margin involvement also affects prognosis . the five recognized histologic types are the well - differentiated , myxoid , round cell , pleomorphic , and dedifferentiated type . the well - differentiated type has good prognosis , with 5-year survival rates of approximately 90% . however , the toxic effects of radiation therapy limit this option by primary treatment modality . research has documented little benefit from adjuvant chemotherapy in well - differentiated low - grade tumors , and partial responses in high - grade diseases in up to 50% of patients , with increased overall survival . as a result , complete surgical resection is the gold standard treatment , which might be curative . in many cases , combined resection of involved organs and vasculatures therefore , the most commonly sacrificed organ is the kidney , followed by the colon , pancreas , major vasculature , and spleen . in this study , we reported on a giant retroperitoneal liposarcoma encasing the entire left kidney and adherent to adjacent structures . furthermore , we described successful organ - preserving surgical removal and discussed the prognosis . although there has been no evidence of recurrence to date , we will continue to observe our patient closely for recurrence , as in other previously published reports .