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 .
 retroperitoneal liposarcoma is a rare tumor . 
 the dimension and weight of liposarcoma are variable ; those over 20 kg are called  
 giant liposarcoma. herein , we report giant retroperitoneal liposarcoma measuring 45 cm in diameter and 25 kg in weight encasing the entire left kidney and adherent to adjacent structures . a 71-year - old woman presented for a regular checkup . 
 image study revealed a huge mass probably indicative of retroperitoneal liposarcoma encasing the entire left kidney and adherent to adjacent structures . 
 we performed an organ - preserving surgical removal . 
 the pathologic report was liposarcoma . at postoperative month 16 , a follow - up ct revealed a locally recurrent tumor . 
 the patient underwent surgical removal of the newly discovered mass . 
 after the second surgery , the patient underwent regular follow - up ct for approximately 12 months , and to date , there has been no evidence of tumor recurrence . 
 high - grade liposarcoma shows sensitivity to radiation therapy . 
 however , the toxic effect of radiation therapy limits this option by treatment modality . 
 the use of chemotherapy is also controversial . as a result , 
 complete resection is the gold standard treatment . here , we report a giant retroperitoneal liposarcoma encasing the entire left kidney and adherent to adjacent structures , describe successful organ - preserving surgical removal and discuss prognosis . 
Introduction
Case Report
Discussion
Statement of Ethics
Disclosure Statement