Nutritional status is a potentially modifiable factor influencing outcomes in retroperitoneal sarcoma (RPS), yet reliable preoperative markers remain underexplored. The prognostic nutritional index (PNI), which combines serum albumin and lymphocyte count, may offer a simple, reproducible tool for risk stratification. We conducted a retrospective cohort study of adult patients undergoing curative-intent resection of primary or recurrent RPS between 2020 and 2024 at a Latin American tertiary center. Patients were stratified by a PNI cutoff of 40, derived via ROC analysis. The primary endpoint was the incidence of major postoperative complications (Clavien-Dindo ≥ III), while secondary endpoints included overall survival (OS) and recurrence-free survival (RFS). Multivariable logistic and Cox regression models were used to assess independent predictors. Among 142 patients, 52.1% had a low PNI (≤ 40). Major complications occurred in 27.6% of patients and were significantly more freq uent in the low-PNI group (37.8% vs. 16.2%, p = 0.006). Low PNI independently predicted significant morbidity (OR 2.72, 95% CI 1.18-6.29, p = 0.018), alongside operative time and intraoperative transfusion. After a median follow-up of 39 months, low PNI was associated with inferior 3-year OS (55% vs. 74%, p = 0.008) and RFS (44% vs. 63%, p = 0.022). On multivariable analysis, low PNI remained a significant predictor of OS (HR 1.98, p = 0.019) and RFS (HR 1.67, p = 0.037). A preoperative PNI ≤ 40 identifies RPS patients at increased risk for significant complications and inferior survival, independent of tumor grade or surgical extent. These findings remained consistent across sensitivity analyses restricted to primary RPS, support the integration of PNI into perioperative risk stratification and nutritional optimization strategies.

The value of pre-operative split renal function radionuclide imaging in multi-visceral resection for retroperitoneal sarcoma: A retrospective cohort study from a high-volume tertiary sarcoma referral centre.

Contemporary Multimodal Management of Primary Retroperitoneal Sarcomas.

Clinical evidence on disease characteristics and outcomes of retroperitoneal sarcoma (RPS) remains limited. Although eribulin was approved for soft tissue sarcomas in Japan in 2016, real-world data on its use for advanced RPS are scarce. We investigated treatment patterns and survival outcomes of patients with RPS, with a particular focus on those receiving eribulin. The database included 118 patients pathologically diagnosed with RPS between January 2000 and August 2025. Clinicopathologic data, including inflammation/nutrition markers and survival outcomes, were analyzed. Among them, 102 (86%) underwent surgical resection of the primary tumor, with a median recurrence-free survival of 20 months and a median overall survival of 9.2 years. Well-differentiated liposarcoma, dedifferentiated liposarcoma, leiomyosarcoma, and undifferentiated pleomorphic sarcoma were the most frequent histologic subtypes. Non-well-differentiated liposarcoma histology, Stage IIIA-IIIB, lower C-reactive protein-albumin-lymphocyte index, and higher modified neutrophil-platelet score were associated with poor postoperative prognosis. Of 44 patients with unresectable RPS who received systemic therapy, 23 (52%) were treated with eribulin. In this group, complete response, partial response, and stable disease rates were 4.3%, 26%, and 35%, respectively. The most common adverse events were decreased neutrophil count (40%), peripheral neuropathy (30%), and dysgeusia (20%). Multivariate analysis showed that non-use of eribulin and undifferentiated pleomorphic sarcoma were independently associated with worse survival in unresectable disease. We separately described outcomes and treatment patterns of patients with resectable and unresectable RPS. Our findings suggest that eribulin should be considered a treatment option for unresectable RPS in clinical practice.

ASO Visual Abstract: Validation of Updated Sarculator Nomogram for Primary Retroperitoneal Sarcoma in the United States.

Most primary retroperitoneal soft tissue tumors are malignant, with liposarcomas and leiomyosarcomas being the most common. However, other sarcomas and benign tumors can also occur in this location. Pathologic evaluation of retroperitoneal sarcomas (RPS) presents unique challenges. Sarcomas are a heterogeneous group with overlapping microscopic features, making accurate classification essential for prognosis and evolving targeted therapies. Core biopsies often capture only a small portion of the tumor, which may result in underestimation of key features such as differentiation, necrosis, and proliferation, leading to undergrading. Surgical management is complicated by the RPS’s tendency to involve adjacent organs. Resections are often large and en bloc, and formalin fixation can obscure anatomic landmarks, making it difficult to identify and assess true surgical margins. In addition to the standard data elements required for cancer staging, specific pathologic features of RPS should be reported to aid in prognosis and treatment planning. This position paper/consensus statement was developed by members of the Trans-Atlantic Australasian Retroperitoneal Sarcoma Working Group (TARPSWG) based on evidence and expert opinion. A detailed description of specimen handling, specimen sampling, and the inclusion of the key diagnostic elements required for an accurate pathology report are provided. The aim of this manuscript is to offer a comprehensive critical reappraisal of the role of pathologic evaluation of surgical specimens in RPS surgery, as well as to propose a standard pathology report to harmonize reporting and facilitate future data collection and interpretation for future research development.

RECIST Responses to Radiation in Retroperitoneal Soft Tissue Sarcoma: When and How Often Do They Occur?

ASO Author Reflections: Refining Management through Time-Learnings from Two Decades of Retroperitoneal Sarcoma Care.

This study aimed to prospectively assess the accuracy of preoperative biopsy in primary retroperitoneal sarcoma (RPS) across sarcoma referral centers. Histological subtype and malignancy grade are key for guiding RPS treatment strategies. However, the accuracy of preoperative biopsy remains uncertain. Data on adult patients with primary localized RPS who underwent preoperative biopsy followed by curative-intent surgery (2017-2020) were collected from the Retroperitoneal Sarcoma Registry. The study aimed to assess concordance between biopsy and surgical specimen histology and grade, using Cohen's kappa statistic. Concordance was also analyzed by center volume (high ≥13 vs. low <13 cases/year). Of 894 enrolled patients, histologic concordance was observed in 87.7% of cases (unweighted κ=0.814; 95% CI, 0.773-0.854). Among 172 tumors initially diagnosed as well-differentiated liposarcomas, 44 (25.6%) were reclassified as dedifferentiated liposarcomas. Grade concordance was observed in 232 of 346 cases (76.1%; weighted κ=0.652; 95% CI, 0.589-0.715), with no difference between computed tomography- and ultrasound-guided biopsies. Concordance by tumor grade was 98.9% (grade 1), 62.1% (grade 2), and 40.2% (grade 3). In dedifferentiated liposarcomas, grade concordance was 59.7% (weighted κ=0.385; 95% CI, 0.292-0.479). High-volume centers showed higher concordance for both histology (κ=0.780) and grade (κ=0.680) compared with low-volume centers (κ=0.622 and 0.564, respectively). While preoperative biopsy for RPS provides satisfactory histologic accuracy, tumor grade is frequently underestimated. This diagnostic inaccuracy may impact treatment decisions, particularly regarding preoperative therapies. Incorporating additional diagnostic factors may improve the accuracy of preoperative assessment.

BackgroundRetroperitoneal tumors represent a variety of rare lesions that can arise either from solid organs (kidney, pancreas, adrenals) or less commonly the mesenchymal soft tissue. Depending on histologic subtype, these malignancies often have a variable clinical presentation and prognosis.Case presentationIn the current series, we present 2 cases: first, a patient with Stage 3 retroperitoneal sarcoma eroding the para-visceral aorta causing rupture; second, a kidney transplant recipient with non-Hodgkin's lymphoma presenting as a ruptured right hypogastric arterial aneurysm.ConclusionWe discuss the caveats and pitfalls in diagnosing and treating these complex tumors including clinical and radiographic presentation.

Retroperitoneal sarcomas (RPS) are rare tumours, primarily treated with surgical resection. However, recurrences are frequent. Combining clinical factors with CT-derived radiomic features could enhance treatment stratification and personalization. This study aims to assess whether radiomic features provide additional prognostic value beyond clinicopathological features in patients with high-risk RPS treated with preoperative radiotherapy. This retrospective study included patients aged 18 or older with non-recurrent and non-metastatic RPS treated with preoperative radiotherapy between 2008 and 2016. Hazard ratios (HR) were calculated using Cox proportional hazards regression to assess the impact of clinical and radiomic features on time to event outcomes. Predictive accuracy was assessed with c-statistics. Radiomic analysis was performed on the high-risk group (undifferentiated pleomorphic sarcoma, well-differentiated/de-differentiated liposarcoma or grade 2/3 leiomyosarcoma). Seventy-two patients were included, with a median follow-up of 3.7 years, the 5-year overall survival (OS) was 67%. Multivariable analysis showed older age (HR: 1.3 per 5-year increase, p = 0.04), grade 3 (HR: 180.3, p = 0.02), and larger tumours (HR: 4.0 per 10 cm increase, p = 0.02) predicted worse OS. In the higher-risk group, the c-statistic for the clinical model was 0.59 (time to distant metastasis (TDM)) and 0.56 (OS). Among 27 radiomic features, kurtosis improved OS prediction (c-statistic 0.69, p = 0.013), and Neighbourhood Gray-Tone Difference Matrix (NGTDM) busyness improved it to 0.73 (p = 0.036). Kurtosis also improved TDM prediction (c-statistic 0.72, p = 0.023). Radiomic features may complement clinicopathological factors in predicting overall survival and time to distant metastasis in high-risk retroperitoneal sarcoma. These exploratory findings warrant validation in larger, multi-institutional studies.

This study aimed to investigate outcome for patients affected by primary retroperitoneal sarcomas (RPS) treated over time at a single large referral institution. The study included all consecutive patients with primary, localized, adult-type soft tissue sarcoma of the retroperitoneum observed and treated at the authors' institution from January 2002 to December 2021. The primary endpoint was overall survival (OS). The secondary endpoints were crude cumulative incidence (CCI) of local recurrence (LR) and distant metastases (DM), and post-recurrence OS. Based on the date of primary surgery, the patients were divided in two groups (2002-2011 and 2012-2021). The study identified 872 patients: 244 treated between 2002 and 2011 (early cohort) and 628 treated between 2012 and 2021 (recent cohort). The median follow-up period was 77.1months (interquartile range [IQR], 41.7-115.4): 136.7months (IQR, 118.1-166.4months) for the early cohort and 59.5months (IQR, 34.1-88.9months) for the recent cohort. At the multivariable analysis, the patients in the recent cohort had significantly better OS. The early cohort had a 5year OS of 61.7% (95% CI, 55.9-68.2%) and a 10year OS of 47.7% (95% CI, 41.7-54.6%), whereas the recent cohort had a 5year OS of 78.8% (95% CI, 75.1-82.6%) and a 10year OS of 64.0% (95% CI, 57.8-70.8%). The recent cohort had fewer distant metastases (hazard ratio [HR], 1.50; 95% CI, 1.06-2.11; p = 0.022) and a similar rate of local recurrences (HR, 1.31; 95% CI, 0.97-1.76; p = 0.080). The 30month post-recurrence OS was 41.9% (95% CI, 34.5-50.9%) in the early cohort and 65.9% (95% CI, 59.5-72.9%) in the recent cohort (p < 0.001). Management of RPS in the recent years has resulted in prolonged OS. These findings establish new standards for historical comparisons of emerging strategies.

The Sarculator nomogram for retroperitoneal sarcoma (RPS) was recently updated to include the variable 'hospital volume', validated using primarily non-U.S.-based patient data. We sought to validate the updated nomogram using U.S. data, examine various cutoffs for high-volume center (HVC) designation (≥ 13 cases per year), and investigate factors that may further improve the nomogram. A nationwide retrospective analysis using the National Cancer Database evaluated patients with RPS from 2010 to 2021. The Cox proportional hazards model was used to evaluate the impact of treatment at HVCs on overall survival (OS) using multiple case/year definitions. A model mimicking Sarculator's parameters was constructed then compared against sequential additions of variables found to be predictive in the initial analysis. A total of 4537 patients were included, 352 of whom were treated at HVCs. Treatment at an HVC using this cutoff was associated with improved OS (hazard ratio [HR] 0.62; 95% confidence interval [CI] 0.43-0.90), whereas there was no association with OS using cutoffs of 10, 7, or 5 cases per year. Female sex (HR 0.81; 95% CI 0.69-0.94) and Charlson Comorbidity Index (CCI) score (HR 1.23; 95% CI 1.02-1.49) predicted improved survival. The addition of the HVC variable to the baseline model improved the fit of the model (likelihood ratio 10.23; p < 0.01) with the C-index going from 0.7126 to 0.7138. The inclusion of sex and CCI score further improved the fit of the model (likelihood ratio 44.41; p < 0.01) and increased the C-index to 0.7187. The updated Sarculator with HVCs defined as ≥ 13 cases per year was validated using U.S.-only patients. The fit of the model was improved with the addition of sex and CCI score variables, and this should be explored in future studies of the Sarculator model.

Extended resection makes it possible to perform a curative resection of conventionally unresectable RPS. However, the rationale and standard procedure for extended resection in RPS remain largely unknown. This study aims to evaluate the efficacy and safety of extended resection using the vascular priority central approach in patients with locally advanced RPS via Semi-Abdominal En Bloc Evisceration (SAEBE). We retrospectively enrolled consecutive RPS patients who underwent SAEBE at our centre between March 2010 and August 2021. We then compared the oncological results with those of patients undergoing non-SAEBE using propensity score matching (PSM) analysis. We developed a detailed procedure for SAEBE surgery, incorporating a central approach with vascular priority, and created a series of matched videos. Histological organ invasion (HOI) was observed in 80.1% (109/136) of cases, and postoperative complications occurred in 55.9% (76/136) of patients. Meanwhile, the 3D model identified HOI risk stratification within the different anatomical regions of the RPS. The RPS was found to be particularly prone to invasion in the front and core cord directions, especially in the colon and kidney. The 30-day mortality rate was 2.9% (four out of 136 patients). Following PSM analysis, SAEBE demonstrated comparable rates of severe postoperative complications and mortality to Non-SAEBE. Furthermore, patients with HOI who underwent SAEBE exhibited a strong trend towards improved overall survival (OS) compared to Non-SAEBE (P=0.042, HR=0.617, 95% CI: 0.378-1.000). The 1-, 3- and 5-year OS rates were 82.6%, 64.1% and 57% for SAEBE patients and 71.9%, 49.8% and 43.1% for non-SAEBE patients, respectively. Short-term safety outcomes are similar, but patients who underwent SAEBE surgery using the vascular priority central approach showed a trend towards improved long-term survival outcomes compared to those who underwent non-SAEBE surgery. Therefore, SAEBE using the vascular priority central approach may represent a promising treatment option for patients with high-risk HOI of locally advanced RPS.

The Two-Decade Experience of Oncovascular Reconstruction in Patients with Retroperitoneal Sarcoma.

Clinically significant delayed gastric emptying after multivisceral resection for retroperitoneal sarcoma: A retrospective cohort study.

Perioperative care in primary retroperitoneal sarcoma surgery: A Hispano-Luso survey on current practices.

Retroperitoneal soft tissue sarcomas (RPS) represent a clinically challenging group of heterogeneous mesenchymal malignancies, predominantly comprising liposarcoma and leiomyosarcoma subtypes. These tumors are characterized by aggressive biological behavior, high rates of local recurrence, and unfavorable clinical outcomes. The nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) serves as a critical regulator of diverse physiological processes, including adipocyte differentiation, glucose/lipid metabolism, inflammatory responses, and immune homeostasis. Emerging evidence demonstrates that dysregulation of PPARγ signaling is closely associated with RPS pathogenesis, particularly in retroperitoneal liposarcoma (RPLS), where PPARγ functional inactivation or aberrant expression correlates significantly with tumor grade and clinical progression. While preclinical studies have demonstrated the therapeutic potential of PPARγ agonists in suppressing tumor proliferation and inducing apoptosis, clinical translation has been limited by intertumoral heterogeneity in drug responsiveness and dose-limiting adverse effects. This review systematically examines the molecular biology of PPARγ and its emerging role in RPS pathobiology, with the aim of informing precision diagnostic and therapeutic strategies for this complex disease entity.

Preoperative Prognostic Nutritional Index as a Predictor of Major Postoperative Complications in Retroperitoneal Sarcoma: A Single-Center Latin American Cohort Study

USP8-Rearranged Mesenchymal Tumors With Myofibroblastic Phenotype: A Comprehensive Clinicopathological, Genetic, and Epigenetic Characterization.