Giant Intra-Abdominal Tumor, Compatible with Liposarcoma: A Case Report and Literature Review

Introduction

Liposarcoma, a rare and heterogeneous group of tumors characterized by a high malignant potential, accounts for about 1% of all adult malignancies [1]. Despite its relatively infrequent occurrence, estimated at 0.5–1 case per 100 000 individuals annually [2], retroperitoneal liposarcoma (RPLS) is the most prevalent subtype among primary retroperitoneal soft-tissue sarcomas, accounting for 41% of all cases [3]. Based on the fifth edition of the WHO Classification of Tumours of Soft Tissue and Bone [4], released in 2020, the subtypes of liposarcomas encompass: atypical lipomatous tumor (ALT), also known as well-differentiated liposarcomas (WDLPS); dedifferentiated liposarcomas (DDLPS); myxoid liposarcomas (MLPS); pleomorphic liposarcomas (PLPS); and myxoid pleomorphic liposarcomas (MPLPS). Notably, WDLPS and DDLPS collectively constitute over 90% of all RPLS [5], thereby receiving significant research attention. Due to the potential space in the retroperitoneal cavity, primary RPLS can grow to very large sizes without causing typical symptoms. The average tumor diameter at diagnosis is 20–25 cm and they weigh 15–20 kg [6], with those weighing more than 20 kg referred to as giant liposarcoma [7].

Most chemotherapy drugs have limited effectiveness against RPLS, while use of radiotherapy is significantly constrained by toxicity concerns [8–10]. Consequently, R0 resection of primary tumors remains the preferred and most effective approach for treatment of RPLS [11].

The prognosis for patients with RPLS following surgical intervention remains dismal. Local recurrence is particularly common, with a 5-year recurrence rate of 61.9% [12]. This alarmingly high recurrence rate not only profoundly impairs patients’ quality of life but also presents significant challenges to medical resources and treatment strategies [13]. Therefore, achieving R0 resection, which refers to the complete removal of the tumor and any potentially involved surrounding tissue, is crucial in minimizing the recurrence rate following surgery [14]. In view of its low incidence and the complexity caused by the close relationship between giant lesions and surrounding vital organs and blood vessels, most clinicians lack sufficient experience in the treatment of such huge tumors [15]. We present a case of an exceptionally large RPLS, measuring 55×35×27 cm with a weight of 26 kg. The tumor was successfully resected, and histopathological examination confirmed dedifferentiated liposarcoma, demonstrated by positive MDM2 and CDK4 immunostaining with a Ki-67 proliferation index ranging from 10% to 30%. Our aim is to provide a comprehensive reference for surgical resection of such giant tumors to our colleagues in the field. We hope that the insights gained from this paper can offer fresh perspectives and inspiration for the diagnosis and treatment of giant RPLS.

Case Report

HISTORY OF PRESENT ILLNESS:

The patient was a 59-year-old man. The chief concern was that physical examination found a solid abdominal mass more than 2 years ago. Abdominal MRI during physical examination in the local municipal hospital indicated that there was a large solid abdominal mass with multiple lymph node metastases in the abdomen, which was considered to be from a retroperitoneal malignant tumor. Within 1 year, he consulted with numerous top medical institutions. However, due to the intricacy of the surgery, which encompassed multiple abdominal organs and crucial blood vessels, no surgery was carried out. Subsequently, the treatment approach was shifted to oral Chinese (and Mongolian) medicine and vascular interventional therapy, but the results were less than satisfactory. The patient felt that his abdomen gradually distending and his physical strength decreased, accompanied by lower-limb edema and dyspnea while supine.

Following admission, a physical examination revealed an abdominal bulge with a circumference of 119 cm in the supine position and conspicuous varicose veins on the abdominal wall (Figure 1A). Additionally, edema was noted in both lower limbs, greater on the right side (Figure 1B). Surgical-related laboratory tests revealed moderate anemia, hypoproteinemia, severe restrictive ventilation dysfunction, and venous thrombosis in the lower extremities. Preoperative CT and 3D imaging demonstrated that the abdominal organs had been compressed, deviating from their original anatomical positions. The abdominal organs were compressed away from the original anatomical position, and the tumor enveloped the left renal arteriovenous and descending colon. Important blood vessels such as the abdominal aorta, inferior vena cava, and iliac vessels were closely involved with the tumor (Figure 1C). We speculated that the tumor originated from the fat sac of the left kidney (Figure 1D). The multidisciplinary team (MDT) consultation in the hospital decided that surgery was expected to result in large intraoperative blood loss. Considering the higher risk of postoperative lower-limb venous thrombosis and pulmonary embolism, an inferior vena cava filter was implanted before surgery, which improved the patient’s general condition.

SURGICAL CHALLENGES:

The retroperitoneal region, being densely populated with vital organs and crucial blood vessels, has a significant risk of inadvertent injury during the dissection of large tumors. Such damage, once incurred, necessitates a highly complex and challenging subsequent treatment course, often involving intricate vascular repairs and restoration of organ functionality. Notably, when the tumor is large and infiltrates critical blood vessels, such as the abdominal aorta, or vital intra-abdominal organs like the intestines and kidneys, the surgical complexity and difficulty surge exponentially. Concurrently, intricate procedures like blood vessel anastomosis, organ excision, and reconstruction are executed, which immensely augment the surgical intricacy and challenge. This intricate procedure requires expertise spanning multiple medical specialties, including vascular surgery, gastrointestinal surgery, and urology. However, with the progressive specialization and refinement in medicine, few surgeons possess sufficient comprehensive knowledge and surgical proficiency in these domains.

PROCEDURE OF SURGERY:

On March 11, 2024, vascular-oriented surgery was performed with R0 resection and total retroperitoneal fat sweeping. After successful anesthetization, the patient was placed in the supine position. Then, after the routine disinfection and towel-laying procedure, we made a combined longitudinal and horizontal ‘+’ incision, in which the longitudinal incision was about 35 cm around the umbilicus, and the horizontal incision was about 30 cm long, and went deep into the abdominal cavity layer by layer. In the surgical field of view, we found a large mass with an intact envelope, soft texture, and good motion. This mass was causing significant pressure on the surrounding organs, and the left kidney was displaced right-forward, the spleen and stomach were displaced upward, the small intestine is pushed to the right posterior abdominal cavity, and the colon is displaced forward. Notably, this tumor was closely associated with part of the colon and its mesangium, even enclosing the arteriovenous vein of the left kidney and part of the descending colon.

According to the predetermined surgical plan, vascular-oriented retroperitoneal massive tumor resection, partial colon resection, left kidney resection, enteroenterostomy, and retroperitoneal total fat dissection were performed (Figure 2A–2I).

The entire operation proceeded smoothly, with a satisfactory anesthetic effect. The resected mass had a complete envelope, with a maximum diameter of approximately 56.5 cm and an impressive weight of 26 kg (Figure 2J–2L).

PATHOLOGY RESULTS:

Pathology investigation revealed a grayish-yellow tumor mass, measuring 55×35×27 cm. The tumor had invaded the intestinal wall and the left kidney, with necrosis evident in the latter (Figure 3A). No tumor tissue was detected on either side of the intestinal duct. Microscopic examination showed aberrant nuclear stromal cells and lipoblasts in the tumor tissue, with spindle-shaped tumor cells observed in certain areas (Figure 3B). Immunohistochemical analysis revealed Ki-67 10–30%, MDM2 scattered positivity, CDK4 positivity, and CD56 positivity. However, S100, CgA, Syn, and WT1 were negative. Molecular pathology indicated MDM2 gene amplification without DDIT3 gene disruption (Figure 3C). Histological features, immunohistochemical markers (positive MDM2/CDK4), and genetic testing (MDM2 amplification) jointly confirmed the diagnosis of DDLPS.

Both DDLPS and WDLPS exhibit amplification of the MDM2 and CDK4 genes. Under the microscope, the morphology of WDLPS closely resembles that of adipose-derived tissues. The typical pathological features of WDLPS include adipocytes of varying sizes separated by fibrous septa interspersed with irregularly-shaped, dense interstitial cells. In contrast, DDLPS demonstrates a sparse arrangement of tumor cells, some of which are spindle-shaped and lack obvious fat vacuoles. A negative DDIT3 test result rules out the possibility of pleomorphic liposarcoma [16,17].

POSTOPERATIVE RECOVERY:

Following the surgery, the patient had stable vital signs, a noticeably flattened abdomen, disappearance of lower-limb edema (Figure 4A), and a significant alleviation of supine dyspnea. A total abdominal CT scan, conducted 14 days after surgery, that the huge retroperitoneal tumor had been removed, the left kidney was absent (Figure 4B), while other abdominal organs resumed their anatomical positions.

The patient’s white blood cell count, indicative of the body’s inflammatory response, temporarily surged after the surgery, typically due to the stress response resulting from surgical trauma. However, as the body gradually healed, the white blood cell count slowly reverted to its normal range. Prior to the surgery, the hemoglobin concentration, a metric for anemia, was successfully maintained above 90 g/L following a series of corrective measures, signifying effective improvement in the anemia status. The albumin levels, reflective of the body’s nutritional condition, were appropriately adjusted before the surgery. Although the albumin level dipped after the surgery, it gradually rebounded over time and eventually stabilized at approximately 35 g/L, indicating gradual improvement in nutritional status [18] (Figure 4C). It is advisable for such patients to undergo follow-up examinations every 3–6 months for the first 2–3 years, then every 6 months for the next 2 years, and annually thereafter [19].

Discussion

Neither chemotherapy, radiotherapy, nor targeted therapy have demonstrated significant improvements in overall patient survival [20–24]. Therefore, surgical treatment has become the standard treatment for RPLS, especially for primary tumors [25].

Early-stage RPLS often lacks distinct clinical manifestations, and by the time of diagnosis, the tumor is typically quite large. A multicenter study conducted in France revealed that the median size of the primary tumor was 15 cm [26]. These tumors are aggressive and expand within the interstitial spaces of tissues, often compressing, encapsulating, or invading adjacent vital organs and blood vessels. In cases of giant RPLS, achieving surgical resection with negative margins presents a significant challenge with a low success rate [27]. To achieve negative incisions, 1 or more organs adjacent to the tumor are excised during surgery, most commonly the kidney, colon, or adrenal gland [28–30], rather than just the tumor tissue on the surface of the organ, resulting in significant surgical difficulty.

Therefore, our center has proposed the VOR surgical approach, in which a first step is accurate location of the boundaries of the main involved blood vessels. Subsequently, along these boundaries, we gradually separate the adhesions between the vessels and the tumor, skeletonizing the vessels, and being sure the tumor has not invaded the subcapsular blood vessels. If the tumor has invaded the crucial subcapsular blood vessels, such as the abdominal aorta, we can employ abdominal aortic replacement and retroperitoneal radical tumor resection to address the issue. Notably, our center has achieved a landmark by successfully executing the world’s first abdominal aortic bypass, abdominal aortic replacement in the upper renal segment, and radical retroperitoneal tumor resection (sci-tech novelty retrieval report number: 202236000Z08X08), ensuring the tumor’s complete removal. VOR significantly reduces intraoperative bleeding and complications, ultimately leading to better treatment outcomes and prognosis for patients. Thorough preoperative evaluations, such as abdominal enhanced CT scans and three-dimensional vascular reconstruction, are crucial in understanding the anatomical relationship between the tumor and abdominal organs and blood vessels. By identifying the anatomical location of the displaced major vessels, we can meticulously plan the surgical approach. This enhances the surgical success rate for RPLS and effectively reduces the incidence of postoperative complications, thus eliminating the ‘giant’ size as a contraindication for surgery.

While complete resection of the primary tumor remains the standard surgical approach for RPLS, novel surgical strategies have continuously emerged as our understanding of the disease deepens. The innovative surgical concept of total (ipsilateral) retroperitoneal lipectomy (TRL) was first proposed by Luo [31]. Recent multi-institutional studies have further confirmed that, among patients with RPLS, TRL offers a superior OS compared to R0 resection [32]. Due to the significant recurrence rate of RPLS, intraperitoneal thermoperfusion chemotherapy has received extensive and sustained research attention. Nevertheless, advances in this field have been sluggish, hindered by potential adverse effects, including intestinal adhesion and obstruction [33]. A cohort study of unilateral tumor and retroperitoneal adipectomy plus intraperitoneal thermoperfusion chemotherapy showed an encouraging 11.61 months longer OS than with conventional R0 resection [34].

The combination of VOR with TRL for giant RPLS, as an innovative surgical approach, theoretically offers new therapeutic possibilities for patients. However, whether it can truly become a safe and effective surgical method remains to be further explored through rigorous clinical research.

Conclusions

The rarity and highly malignant nature of RPLS significantly hinder the depth of research into this disease, thus limiting comprehensive understanding. The surgical techniques for RPLS have undergone continuous refinement, resulting in a significant improvement in postoperative survival rates and a reduction in surgical complications. However, in the ongoing research on liposarcoma, there remains a pressing need to explore innovative breakthroughs in non-surgical areas to further broaden the spectrum of therapeutic options.