Soft-tissue sarcomas are relatively rare with approximately 8,600 new cases annually and represent less than 1% of all newly diagnosed malignancies in the United States. Retroperitoneal sarcomas are malignant tumors arising from mesenchymal cells, which are usually located in muscle, fat, and connective tissues. One-third of malignant tumors located in the retroperitoneum are sarcomas, and approximately 15% of soft tissue sarcomas arise in the retroperitoneum. [1] According to the World Health Organization (WHO), soft-tissue liposarcomas are categorized into five distinct histological subtypes: well-differentiated, dedifferentiated, myxoid, pleomorphic and mixed type. Retroperitoneal sarcomas have varying clinical courses depending on their histological subtype and grade. [1] [2]

The pathologic diagnosis of liposarcoma rests on the identification of lipoblasts in a milieu of supporting histomorphologic features. The well-differentiated liposarcoma is a low-grade neoplasm which can present as five histological variants: lipoma-like, sclerosing, inflammatory, spindle cell and liposarcoma with meningothelial whorls. The treatment of choice is complete surgical excision. According to Stoeckle et al., there are no survival benefits of adding adjuvant radiotherapy at this time for a resected well-differentiated retroperitoneal liposarcoma. [3]

A 67-year-old female was presented to the gynecologist for screening Pap smear. The patient complained at that time of right upper quadrant abdominal pain. Her past medical history was significant for hypertension, asthma, and hyperlipidemia which were well-controlled and there was no significant family history. She had a previous midline scar from a total abdominal hysterectomy with bilateral salpingo-oophorectomy for fibroid. On examination, her abdomen was very obese (BMI 44.8) with right upper quadrant tenderness. No mass was palpated and she had a reducible incisional hernia. Abdominal ultrasound revealed a large heterogeneous left flank mass and cholelithiasis. Origin of the mass was uncertain, computed tomography (CT) scan was recommended for further assessment. She was subsequently referred to surgery for management and imaging studies. The CT scan of abdominal showed a large retroperitoneum mass with displacement of the retroperitoneal organs. (Figure 1A–B) The origin and blood supply of the mass could not be determined on the CT scan and magnetic resonance imaging (MRI) scan was recommended, revealing a large complex retroperitoneal cystic mass adherent to the left kidney which extended from the splenic hilum inferiorly to the left lower abdomen. (Figure 2)

The case was presented at the multidisciplinary tumor board. The recommendation was to proceed with surgery first. Neoadjuvant chemotherapy was not recommended as there was no tissue diagnosis. After discussion with the patient and her family, she underwent an exploratory laparotomy with en-bloc resection of the retroperitoneal tumor. At surgery, there was a left retroperitoneal mass as per, adherent to the left kidney, but separate from the spleen, pancreas, and colon. The mass was resected en-bloc with the kidney. The gallbladder was removed for chronic cholelithiasis which was symptomatic and her incisional hernia was repaired. Her postoperative course was uneventful.

The mass was well circumscribed and globular composed of fleshy homogeneous yellow tan tissue. The tumor weighed 1670 grams and measured 30x25x15 cm. (Figure 3) Routine tissue stain demonstrated a well-differentiated liposarcoma, characterized by its hypocellularity, nuclear pleomorphic atypia and delicate vascularity. The tumor was composed of myxoid stroma with increase microvascularity and atypical adipocytes. Some of these adipocytes have a single vacuole and others demonstrated a floret giant cell configuration. (Figure 4) An atypical lipoblast was demonstrated in. (Figure 5) This large cell had an enlarged nucleus, irregular in shape, with variably clumped chromatin and the cytoplasm contained numerous vacuoles.

The stroma was variably fibrillar with areas of abundant ground substance. A mild inflammatory infiltrate was present with a significant quantity of plasma cells. Final pathology revealed the tumor to be a low grade, well-differentiated, stage T2bG1N0M0 retroperitoneal liposarcoma. The medical and radiation oncologists suggested observation and interval follow-up for surveillance.

Retroperitoneal tumors are an extremely heterogeneous group of neoplasms, 85% of which are malignant. Liposarcomas constitute between 45–55% of retroperitoneal masses. [4] Age at presentation is younger compared with most other malignancies, with many being diagnosed.

Between 54–65 years of age [5]. There is an equal male/female ratio. [1] The distribution of soft tissue sarcomas by anatomic site can be found in an article by Lawrence et al.[6]

Retroperitoneal sarcomas present 80% of the time as an asymptomatic abdominal mass. Symptoms can also be related to mass effect or local invasion which may lead to pain, gastrointestinal obstruction, feelings of early satiety, and weight loss. In addition, neurologic and muscular skeletal symptoms are referred to the lower extremities. [7]

Histopathologic variety is the main prognostic factor. Five histologic types are recognized. Well differentiated liposarcoma represents around 30% like our case and has the best prognosis. The myxoid type is the most frequent liposarcoma, constituting around 50% of all tumors. It has a less favorable progression, as it often recurs early. The pleomorphic, round cell and undifferentiated types display the worst prognosis. [4]

After a physical examination CT scan provides an excellent understanding of the relationship between nearby structures and is critical to preoperative planning. A patient presenting with a palpable abdominal mass, should be have a high-resolution, thin-cut CT scan with intravenous and oral contrast since these images allow for further distinction between intra-abdominal and retroperitoneal structures. This allows a discussion of the need for biopsy if indicated, the operative plan, and the preparedness of the operative team, as well as a discussion with the patient regarding the risks and benefits. The differential diagnosis includes a primary neoplasm arising from a retroperitoneal visceral structure (e.g., pancreas, adrenal glands, kidneys, and duodenum), a retroperitoneal sarcoma, a lymphoma, or a metastatic lesion. [5]

The optimal treatment for patients with localized, resectable retroperitoneal sarcomas is surgery with gross and microscopically negative margins. Complete surgical resection frequently requires en-bloc resection of adjacent viscera. [8] The kidney was the most frequently resected organ (36%) followed by segmental resection of the large bowel, spleen, and pancreas. [9]

The addition of adjuvant radiation therapy to surgical resection is associated with both a reduced risk of local recurrence and a longer recurrence-free interval. However, it does not improve overall survival. Studies have demonstrated the advantages of preoperative radiotherapy in the management of marginally resectable retroperitoneal sarcomas. The benefits of pre-operative radiation are multiple. [3] [10] It allows for the gross tumor volume to be readily definable for accurate treatment planning. Moreover, the tumor displaces radiosensitive viscera. Thus, no adhesions and tethering of bowel to the tumor bed can occur and the tumor is treated in situ.

Another treatment modality is intra-operative radiotherapy (IORT) which is targeted to a specific region allowing for maximum doses of radiation to the tumor bed. Studies show that IORT improves tumor control in the field. However, it does not influence recurrence-free or overall survival rates. [9] [10]

The review of the literature emphasizes that the management of retroperitoneal sarcomas consists of complete resection of the tumor followed by adjuvant radiotherapy reduce local recurrence but does not affect overall survival and combined with surveillance for early detection of recurrence or metastases. Imaging studies are essential for proper preoperative planning and allow assessment of respectability prior surgery; preoperative radiotherapy can be considered in patients with questionably resectable tumors. Contrast-enhanced computed tomography scan and magnetic resonance imaging were valuable aids in our case. The patient should be closely followed with regular physical examinations and imaging studies such as chest X-rays and computed tomography scans. Our patient continues to follow-up for surveillance and is doing well.

1. Windham TC, Pisters PW. Retroperitoneal sarcomas. Cancer Control 2005;12(1):36–43.   [Pubmed]    
2. Kawano R, Nishie A, Yoshimitsu K, et al. Retroperitoneal well-differentiated inflammatory liposarcoma: a diagnostic dilemma. Radiat Med 2008;26(7):450–3.   [CrossRef]   [Pubmed]    
3. Stoeckle E, Coindre JM, Bonvalot S, et al. Prognostic factors in retroperitoneal sarcoma: a multivariate analysis of a series of 165 patients of the French Cancer Center Federation Sarcoma Group. Cancer 2001;92(2):359–68.   [CrossRef]   [Pubmed]    
4. Leão P, Vilaça S, Oliveira M, Falcão J. Giant recurrent retroperitoneal liposacrcoma initially presenting as inguinal hernia: review of literature. Int Journal of Surgery case Report 2012;3(3):103–6.   [CrossRef]   [Pubmed]    
5. John E Mullinax, Jonathan S Zager, Ricardo J Gonzalez. Current Diagnosis and Management of Retroperitoneal Sarcoma. Cancer Control 2011;18(3):177–87.   [Pubmed]    
6. Lawrence W Jr, Donegan WL, Natarajan N, Mettlin C, Beart R, Winchester D. Adult soft tissue sarcomas. A pattern of care survey of the American College of Surgeons. Ann Surg 1987;205(4):349–59.   [CrossRef]   [Pubmed]    
7. Wanchick K, Lucha P. Dedifferentiated retroperitoneal liposarcoma presenting as lower gastrointestinal bleeding, a case report and review of the literature. Military Medicine 2009;174(3):328–30.   [Pubmed]    
8. Pisters PW, O'Sullivan B. Retroperitoneal sarcoma: combined modality treatment approaches. Curr Opin Oncol 2002;14(4):400–5.   [CrossRef]   [Pubmed]    
9. Hassan I, Park SZ, Donohue JH, et al. Operative management of primary retroperitoneal sarcomas: a reappraisal of an institutional experience. Annals of Surgery 2004;239(2):244–50.   [CrossRef]   [Pubmed]    
10. Mendenhall WM, Zlotecki RA, Hochwald SN, Hemming AW, Grobmyer SR, Cance WG. Retroperitoneal soft tissue sarcoma. Cancer 2005;104(4):669–75.   [CrossRef]   [Pubmed]