Giant Retroperitoneal Liposarcoma Without Organ Invasion: A Rare Case Report

Introduction

Liposarcoma is a malignant soft tissue sarcoma arising from adipocytic precursor cells, and represents one of the most common histologic subtypes of soft tissue sarcomas [1–3]. These tumors most frequently occur in the retroperitoneum and extremities [1,2]. Retroperitoneal liposarcoma can affect individuals of all ages, with a peak incidence between 40 and 60 years and a slight male predominance. The reported incidence of retroperitoneal sarcoma is approximately 3 to 4 cases per million population annually [1,3].

Due to the large potential space of the retroperitoneum, liposarcomas may reach considerable dimensions before becoming clinically apparent. Although there is no universally accepted definition of “giant” retroperitoneal liposarcoma, several dimensional criteria have been proposed. Some authors define tumors measuring ≥20–25 cm as giant, reflecting the substantial tumor burden that can accumulate within the retroperitoneal space [4]. Other studies apply a more stringent definition, considering tumors ≥30 cm in diameter or weighing ≥20 kg as giant retroperitoneal liposarcomas [5]. In a recent systematic review by Santangelo et al [5], including 157 reported cases of giant retroperitoneal liposarcoma, tumor sizes ranged from 15 to 80 cm. Lesions exceeding 30 cm were commonly categorized as giant, while those larger than 45 cm were sometimes described as enormous. Reported tumor weights ranged from 2.5 kg to 98 kg, and no standardized weight threshold has been established due to histological variability [5]. In this context, the tumor in our case measured 28×24×23 cm and weighed 10 kg, representing a very large retroperitoneal liposarcoma approaching the commonly cited dimensional criteria used to define giant tumors.

According to the World Health Organization (WHO) 2020 classification, liposarcomas are divided into 5 histological subtypes: well-differentiated, dedifferentiated, myxoid, pleomorphic, and myxoid pleomorphic [6]. Prognosis largely depends on histological subtype. Well-differentiated retroperitoneal liposarcoma generally has a favorable prognosis with a 5-year overall survival approaching 80–90%, whereas dedifferentiated liposarcoma is associated with substantially worse outcomes, with reported 5-year survival rates between approximately 40% and 55% [7].

Diagnosis relies primarily on cross-sectional imaging such as computed tomography (CT) and magnetic resonance imaging (MRI), with definitive confirmation obtained through histopathological examination and immunohistochemistry. Management is multidisciplinary and primarily surgical, while the roles of radiotherapy and systemic therapy remain selective and are often reserved for specific clinical situations [3,8].

We report a case of a giant retroperitoneal liposarcoma and discuss the diagnostic challenges and surgical management of such tumors, with particular attention to the potential role of organ-preserving resection in selected cases within current clinical practice.

Case Report

A 61-year-old woman presented with progressive abdominal distension over the preceding 6 months, accompanied by mild abdominal discomfort, nausea, dyspepsia, and exertional dyspnea. No weight loss or constitutional symptoms were reported. Physical examination revealed a markedly increased abdominal circumference and a diffuse, firm mass with limited mobility. The patient had no prior oncologic treatment and reported no family history of similar tumors or known hereditary syndromes. Her past medical history was notable for a salpingo-oophorectomy performed 12 years earlier. To further evaluate the abdominal mass, abdominopelvic MRI was performed.

The abdominopelvic MRI, performed in October of 2025, including T1-weighted, T2-weighted, and T2 fat-suppressed sequences with intravenous gadolinium contrast, revealed a giant retroperitoneal (extraperitoneal) mass measuring approximately 28×23.6×24 cm (craniocaudal×anteroposterior×laterolateral). The lesion exhibited heterogeneous signal intensity, predominantly adipose with interspersed non-lipomatous solid areas, appearing iso-to hyperintense on T2-weighted and fat-suppressed sequences, and iso- to hypointense on T1-weighted images. Based on these imaging features, dedifferentiated liposarcoma was initially suspected.

The mass originated from the left pelvis and extended into the left perirenal and anterior pararenal spaces. The mass abutted the left kidney, abdominal aorta, and inferior vena cava without evidence of parenchymal or vascular invasion, and contacted the duodenum, small bowel, and hepatic flexure of the colon without mural infiltration. Major abdominal vessels remained patent. The liver, spleen, pancreas, and biliary system demonstrated normal morphology and signal characteristics. The left adrenal gland harbored a 3.4 cm adenoma, while the right adrenal gland was unremarkable. The kidneys and urinary tract appeared normal, and the uterus and ovaries had been surgically removed previously. No secondary metastatic lesions were identified in the bones or lungs (Figure 1).

Contrast-enhanced abdominopelvic CT with arterial and venous phases, performed in November of 2025, confirmed the findings observed on MRI. The only additional observation was mild dilation of the left kidney and proximal ureter, with preserved renal parenchyma and no evidence of hydronephrosis (Figure 2).

Ultrasound-guided core needle biopsy of the abdominal mass was performed and submitted for histopathological and immunohistochemical analysis. Tumor cells demonstrated strong positivity for vimentin, focal positivity for S100, and a low Ki-67 proliferation index, whereas CD34, smooth muscle actin (SMA), desmin, and cytokeratin AE1/AE3 were negative. These findings were suggestive of well-differentiated liposarcoma, and complete surgical excision was recommended. MRI initially suggested dedifferentiated liposarcoma due to the presence of solid non-lipomatous areas; however, the core needle biopsy findings favored a well-differentiated subtype.

Two days after the CT and biopsy, the patient was admitted to the Department of Abdominal Surgery at the University Clinical Centre of Kosovo. She had good baseline functional status and was independent in activities of daily living, with an Eastern Cooperative Oncology Group (ECOG) performance status of 1. The patient had no significant medical comorbidities and was classified as having American Society of Anesthesiologists (ASA) physical status II during the preoperative anesthetic evaluation. Preoperative clinical assessment and laboratory investigations demonstrated normal renal and hepatic function, normal inflammatory markers, and no metabolic abnormalities.

Two days after admission to the hospital, the patient underwent surgery. Under general anesthesia, a midline supra- and infraumbilical laparotomy was performed, resulting in complete excision of the retroperitoneal liposarcoma. The operative time was approximately 200 minutes, with an estimated blood loss of 500 mL. Intraoperatively, the mass was found to arise from retroperitoneal adipose tissue and to displace adjacent organs without evidence of direct organ or vascular invasion. The tumor appeared mobile and well encapsulated. Careful exploration demonstrated preserved dissection planes between the mass and surrounding structures, including the left kidney, major abdominal vessels, and bowel loops. Based on these findings, organ-preserving resection was considered oncologically appropriate, and multivisceral resection was not required. The tumor was successfully mobilized and removed through meticulous blunt and sharp dissection while preserving the adjacent organs. The excised specimen weighed 10 kg (Figure 3). No intraoperative complications were observed, and no blood transfusion was required. The postoperative course was largely uneventful. On postoperative day 3, the patient developed low-grade fever accompanied by mild leukocytosis and elevated C-reactive protein levels. Antibiotic therapy was initiated, corresponding to a Grade II complication according to the Clavien–Dindo classification.

Multiple representative sections of the excised retroperitoneal mass were examined for histopathological analysis. Histopathological examination revealed a tumor composed predominantly of mature adipocytes showing variation in adipocyte size and mild cytologic and nuclear pleomorphism. The stroma contained collagenous bands with scattered atypical lipoblasts, and focal areas of myxoid change were identified, consistent with well-differentiated liposarcoma with predominantly sclerosing features. The tumor was surrounded by a fibrous capsule. No vascular invasion was observed (V0), and surgical margins were free of tumor (R0). According to American Joint Committee on Cancer (AJCC) classification, the tumor was staged as pT4N0M0 (Stage IB) (Figure 4).

During hospitalization, the patient received antibiotics, a proton pump inhibitor (PPI), nonsteroidal anti-inflammatory drugs (NSAIDs), and anticoagulants. Supportive therapy included human albumin to correct postoperative hypoalbuminemia and fluid shifts following large tumor resection, as well as fresh frozen plasma to address mild postoperative coagulation disturbances. She was discharged after 8 days in good clinical condition. Continuing treatment consisted of home therapy with antibiotics, PPI, and NSAIDs.

As follow-up, the surgeon recommended whole-body scintigraphy. Whole-body bone scintigraphy performed 3 hours after intravenous administration of 15 mCi of Technetium-99m–labeled methylene diphosphonate (99mTc-MDP) demonstrated no evidence of skeletal metastases. Symmetric tracer uptake observed in the knees and feet was consistent with degenerative changes (Figure 5).

Postoperative abdominopelvic MRI was performed approximately 45 days after surgery. Imaging findings were consistent with complete surgical resection of the retroperitoneal mass. In the left perirenal region, a heterogeneous collection measuring approximately 9 cm craniocaudally and 5×4 cm in the axial plane was noted, exhibiting hyperintensity on T2/STIR sequences, a fatty component on T1 that was suppressed on T1 fat-saturated sequences, and mild marginal enhancement following contrast administration. No diffusion restriction was observed on apparent diffusion coefficient/diffusion-weighted imaging (DWI/ADC) sequences (Figure 6). There was no evidence of renal parenchymal infiltration or involvement of adjacent structures, and no pathological abdominal lymph nodes were identified. Findings in other abdominal and extra-abdominal organs remained unchanged compared with preoperative MRI. Considering the complete surgical resection confirmed on histopathological examination (R0, V0), the absence of diffusion restriction, and the lack of nodular or solid enhancing components, the imaging findings favored postoperative changes, most likely representing a resolving serohemorrhagic hematoma rather than residual or recurrent disease (Figure 6).

To further evaluate the postoperative MRI findings and exclude residual disease, a positron emission tomography (PET)/CT scan was performed in January of 2026, following intravenous administration of 7.8 mCi 18F-Fluorodeoxyglucose (FDG) in the left arm. Mild-to-moderate FDG uptake was observed at the surgical site, with a maximum standardized uptake value (SUVmax) of 3.17, comparable with background hepatic activity (SUVmax 3.55) and consistent with postoperative inflammatory changes (Figure 7). The liver was used as reference, demonstrating an SUVmax of 3.55 g/mL. No abnormal FDG uptake was noted in the abdominal, pelvic, or inguinal lymph nodes. Both kidneys demonstrated physiologic tracer distribution without evidence of pathological uptake. No hypermetabolic lesions were identified in other intra-abdominal or extra-abdominal organs. Incidental findings included mild FDG uptake in the left ocular bulb and focal uptake in the thyroid gland, likely representing inflammatory processes (Figure 7).

The oncology team did not recommend adjuvant therapy. At the most recent follow-up, approximately 3 months postoperatively, the patient remained asymptomatic, with no clinical or imaging evidence of recurrence or residual disease. However, retroperitoneal liposarcoma is known for its tendency toward late local recurrence; therefore, longer-term follow-up is necessary. The patient will remain under regular clinical and imaging follow-up.

Discussion

Sarcomas are rare primary mesenchymal tumors, representing less than 1% of all cancers. About 10% to 15% occur in the retroperitoneum, where liposarcoma is the most frequent subtype [1,3]. Retroperitoneal liposarcoma affects all ages but is more common between 40 and 60 years, with a male predominance. The reported incidence is 3 to 4 cases per million population [1,3]. Our patient was a 61-year-old woman.

According to the WHO 2020 classification, liposarcomas are categorized into 5 major histological subtypes: well-differentiated, dedifferentiated, myxoid, pleomorphic, and myxoid pleomorphic [6]. Among retroperitoneal liposarcomas, well-differentiated and dedifferentiated subtypes are the most frequently encountered. Histological subtype represents the most important prognostic determinant for recurrence, metastatic potential, and overall survival. Five-year overall survival has been reported to be approximately 80–90% for well-differentiated liposarcomas, compared with roughly 40–55% for dedifferentiated liposarcomas [7]. In our patient, histopathological findings were consistent with well-differentiated liposarcoma, suggesting a relatively favorable prognosis.

Well-differentiated liposarcoma can be classified into 3 histological subtypes: lipoma-like, sclerosing, and inflammatory. In contrast, dedifferentiated liposarcoma is characterized by the presence of a non-lipogenic sarcomatous component arising within or adjacent to a well-differentiated liposarcoma and may show several morphological patterns, including spindle cell, pleomorphic, or heterologous differentiation such as osteosarcomatous, chondrosarcomatous, or leiomyosarcomatous features [7].

Due to the large anatomical space of the retroperitoneum, these tumors can reach substantial sizes before becoming clinically evident. Many patients remain asymptomatic until the mass causes compression of adjacent organs or is detected incidentally. In roughly 80% of cases, symptoms include abdominal pain and a sensation of heaviness, with a firm, non-tender mass often palpable on examination. Compression may also cause lower extremity edema, urinary frequency changes, or nonspecific gastrointestinal complaints such as early satiety or visceral pain [1,3]. In our patient, symptoms were mild, with progressive abdominal distension and mild discomfort, reflecting the typically insidious presentation of retroperitoneal tumors and consistent with literature reports.

The diagnosis of retroperitoneal liposarcoma requires integration of imaging and histopathology. MRI provides superior delineation compared with CT, accurately assessing tumor size, relationships with adjacent organs and vessels, and differentiating adipose from non-adipose components, which aids in grading and preoperative planning [3,8]. In our patient, MRI precisely characterized a 28×23.6×23 cm mass without evidence of organ or vascular invasion. Image-guided core needle biopsy confirmed a well-differentiated liposarcoma, enabling safe, complete surgical excision with negative margins (R0) and organ preservation.

Preoperative core needle biopsy is generally considered a safe and useful diagnostic tool in selected cases, although theoretical concerns about tumor seeding remain. Determination of histologic subtype and tumor grade before surgery is essential for planning and considering potential neoadjuvant therapies. Large tertiary-center studies report a very low risk of tumor dissemination after biopsy, ranging from approximately 0.37% to less than 2% [9].

Fluorescence in situ hybridization (FISH) for MDM2 amplification, a commonly used molecular method for confirming well-differentiated liposarcoma and distinguishing it from benign lipomatous tumors, was not available in our institution and therefore could not be performed [7]. The absence of molecular confirmation represents a limitation of the present report. The immunohistochemical profile, characterized by diffuse vimentin positivity, focal S-100 expression, a low Ki-67 proliferation index, and negativity for AE1/AE3, SMA, and desmin, supported the diagnosis. In particular, negative staining for AE1/AE3 helped exclude epithelial malignancies such as carcinoma, while the absence of SMA and desmin argued against smooth muscle tumors such as leiomyosarcoma [10].

Histopathological examination demonstrated mature adipocytic proliferation with atypical stromal cells and identifiable lipoblasts, findings that are commonly described in well-differentiated liposarcoma. No evidence of a high-grade non-lipogenic sarcomatous component, marked cellular pleomorphism, tumor necrosis, or increased mitotic activity was identified, features that are typically associated with dedifferentiated liposarcoma. The tumor was surrounded by a fibrous capsule and was completely excised with clear surgical margins (R0) without vascular invasion (V0). Intraoperatively, the mass displaced rather than infiltrated adjacent organs and tissues. Although imaging demonstrated non-lipomatous areas that could raise suspicion for dedifferentiated liposarcoma, the final diagnosis was based primarily on histopathological findings in conjunction with the immunohistochemical profile and overall clinicopathological correlation, favoring well-differentiated liposarcoma.

The standard treatment for well-differentiated retroperitoneal liposarcoma is complete surgical excision with negative margins (R0) [8]. In cases with local invasion, multiorgan resection, often including the kidneys or bowel, may be required. En bloc resection with negative margins remains the cornerstone of treatment for retroperitoneal sarcoma and is associated with improved oncologic outcomes, as emphasized in contemporary consensus recommendations [2]. Locoregional recurrence remains the main challenge in retroperitoneal liposarcoma. Contemporary surgical strategies remain the subject of ongoing debate. While some centers advocate extended multivisceral resection to improve local control, particularly in well-differentiated tumors [11], current clinical recommendations emphasize a selective organ-preserving approach, in which adjacent organs are resected primarily when there is clear evidence of direct tumor invasion, balancing oncologic radicality with the goal of reducing surgical morbidity [8]. In the present case, intraoperative assessment demonstrated that the tumor displaced adjacent organs without clear evidence of direct invasion. This allowed safe dissection along anatomical planes and complete tumor removal with negative margins. Preservation of uninvolved organs may reduce surgical morbidity and maintain postoperative organ function while still achieving adequate oncologic resection, particularly in well-differentiated retroperitoneal liposarcomas, which often grow while displacing rather than infiltrating adjacent structures. Microscopically negative margins remain the most important prognostic factor. The role of adjuvant radiotherapy and chemotherapy is limited and typically reserved for high-grade tumors, positive margins, or recurrence, with uncertain impact on long-term survival [8]. Immunotherapy and targeted therapy are under investigation but have shown limited efficacy to date [12]. In our patient, no adjuvant therapy was administered.

Giant retroperitoneal liposarcomas exceeding 30 cm have been rarely reported in the literature, and many of these cases require multiorgan resection to achieve negative margins. In many reported cases, adjacent organs are involved or displaced, necessitating resection of surrounding structures during surgery. Cases in which tumors larger than 30 cm are completely resected without organ involvement appear to be uncommon, providing a valuable comparison for our patient. Among published reports, Rachman and Hardja (2022) described a case in which a tumor was completely resected with negative margins without removal of adjacent organs, suggesting that organ-preserving complete resection in such large tumors may be uncommon

Conclusions

This case demonstrates that even a giant well-differentiated retroperitoneal liposarcoma exceeding 28 cm can be successfully resected with negative margins (R0) while preserving adjacent organs when they are displaced rather than infiltrated. Preoperative imaging and image-guided core needle biopsy play an important role in diagnostic evaluation and surgical planning in selected cases. Postoperative MRI, whole-body scintigraphy, and PET/CT showed no evidence of residual or secondary disease. Complete surgical resection with microscopically negative margins remains the cornerstone of treatment for retroperitoneal liposarcoma, while the role of adjuvant radiotherapy and chemotherapy remains limited and depends on histologic subtype and individual patient characteristics. However, the short follow-up period and the absence of molecular confirmation represent important limitations of this report, and longer follow-up is required to better assess long-term oncologic outcomes [13].