Explainable machine learning predicts survival of retroperitoneal liposarcoma: A study based on the SEER database and external validation in China.

OBJECTIVE: We have developed explainable machine learning models to predict the overall survival (OS) of retroperitoneal liposarcoma (RLPS) patients. This approach aims to enhance the explainability and transparency of our modeling results. METHODS: We collected clinicopathological information of RLPS patients from The Surveillance, Epidemiology, and End Results (SEER) database and allocated them into training and validation sets with a 7:3 ratio. Simultaneously, we obtained an external validation cohort from The First Affiliated Hospital of Naval Medical University (Shanghai, China). We performed LASSO regression and multivariate Cox proportional hazards analysis to identify relevant risk factors, which were then combined to develop six machine learning (ML) models: Cox proportional hazards model (Coxph), random survival forest (RSF), ranger, gradient boosting with component-wise linear models (GBM), decision trees, and boosting trees. The predictive performance of these ML models was evaluated using the concordance index (C-index), the integrated cumulative/dynamic area under the curve (AUC), and the integrated Brier score, as well as the Cox-Snell residual plot. We also used time-dependent variable importance, analysis of partial dependence survival plots, and the generation of aggregated survival SHapley Additive exPlanations (SurvSHAP) plots to provide a global explanation of the optimal model. Additionally, SurvSHAP (t) and survival local interpretable model-agnostic explanations (SurvLIME) plots were used to provide a local explanation of the optimal model. RESULTS: The final ML models are consisted of six factors: patient's age, gender, marital status, surgical history, as well as tumor's histopathological classification, histological grade, and SEER stage. Our prognostic model exhibits significant discriminative ability, particularly with the ranger model performing optimally. In the training set, validation set, and external validation set, the AUC for 1, 3, and 5 year OS are all above 0.83, and the integrated Brier scores are consistently below 0.15. The explainability analysis of the ranger model also indicates that histological grade, histopathological classification, and age are the most influential factors in predicting OS. CONCLUSIONS: The ranger ML prognostic model exhibits optimal performance and can be utilized to predict the OS of RLPS patients, offering valuable and crucial references for clinical physicians to make informed decisions in advance.

Low-grade malignant peripheral nerve sheath tumour presenting as retroperitoneal spindle cell neoplasm.

Retroperitoneal spindle cell neoplasms are diagnostically challenging. Malignant peripheral nerve sheath tumours (MPNSTs) can sometimes present as sporadic primary retroperitoneal tumours. MPNSTs are usually high-grade and highly aggressive tumours and are associated with a poor prognosis. Low-grade MPNSTs are very rarely described. This current case report describes a case of sporadic primary low-grade MPNST presenting as retroperitoneal spindle cell neoplasm. The diagnosis, imaging and immunohistopathological findings, as well as its successful surgical management, are presented.

Large retroperitoneal lymphangioma.

Abnormal cystic lymphangioma is a rare, benign tumour of lymphatic origin that often presents with subtle clinical symptoms. A man in his 20s sought medical attention for a progressively tender mass located in the right lower quadrant. Following ultrasound and CT imaging, surgical pathology confirmed the presence of abnormal cystic lymphangioma. This case is noteworthy because of the patient's young age and the retroperitoneal location. An exploratory laparotomy was performed, mitigating the risk of recurrence. In the future, if imaging identifies a cystic mass, consideration of abnormal cystic lymphangioma within the differential diagnosis is imperative. Despite its predominantly subtle symptoms and non-malignant nature, the mass effect by the abnormal cystic lymphangioma can compromise surrounding structures. Overall, clinicians confronted with a cystic mass should adopt a comprehensive diagnostic approach, encompassing abnormal cystic lymphangioma in the differential diagnosis due to its unknown and complex nature.

111 In-Pentetreotide-Guided Radiosurgery for Intraoperative Localization of Retroperitoneal Nodal Metastasis in a Patient With Ileal Neuroendocrine Tumor.

ABSTRACT: 64 Cu-DOTATATE PET/CT of a 44-year-old man with an ileal neuroendocrine tumor demonstrated the primary tumor, local nodal metastases, and a pericaval nodal metastasis. Localization of the pericaval node during surgery may be difficult, thus 4.4 mCi of 111 In-pentetreotide was administered before surgery to assist with localization and resection. At surgery, the pericaval nodal metastasis was readily detected by gamma probe, which could then be resected and pathologically proven to be a metastasis. This demonstrates the use of somatostatin receptor-targeted imaging for intraoperative localization of an otherwise difficult to surgically localize metastasis. Without intraoperative somatostatin receptor-targeted radiosurgery, disease may have been incompletely resected.

Intraoperative radiofrequency ablation for unresectable abdominal paraganglioma: a case report.

For pheochromocytoma and paraganglioma (PPGL), the efficacy of percutaneous ablative therapies in achieving control of metastatic tumors measuring <3 cm had been demonstrated in only few reports, and intraoperative radiofrequency ablation (RFA) of locally invasive primary PPGLs has not been reported. We presented the case of a 31-year-old man who had a 9-cm functioning unresectable PPGL. He was treated with 13 cycles of cytotoxic chemotherapy without objective tumor response, according to the Response Evaluation Criteria in Solid Tumors (RECIST). Subsequently, magnetic resonance imaging revealed a 9.0 × 8.6 × 6.0-cm retroperitoneal mass that extended to the inferior portion of the inferior vena cava, the inferior mesenteric artery, and the infrarenal aorta. Biochemical evaluation demonstrated high level of plasma normetanephrine (20.2 nmol/L, normal range <0.9 nmol/L). Genetic investigation showed the germline pathogenic variant c.1591delC (p. Ser198Alafs*22) in the SDHB gene. I131-metaiodobenzylguanidine scintigraphy was negative and Ga68-dotatate PET-CT scan showed high tumor uptake without distant metastases. On open laparotomy, tumor debulking was not possible. Therefore, intraoperative RFA was performed by a highly experienced team of interventional radiologists. At 12 months after the RFA, the tumor volume decreased from 208 to 45 mL (78%), plasma normetanephrine decreased from 20.2 to 2.6 nmol/L (87%), and the doxazosin dose was reduced from 16 to 8 mg/day. To our best knowledge, this was the first report on intraoperative RFA that markedly reduced the size of a large primary unresectable PPGL, along with clinical and biochemical responses.

Diagnosis and treatment of malignant retroperitoneal mesothelioma: A case report.

RATIONALE: Malignant peritoneal mesothelioma (MPM) is a rare clinical disease. Although there are several reports describing intraperitoneal mesothelioma of the lung, liver, and intestine, retroperitoneal mesothelioma is, to our knowledge, very rare and rarely reported. In recent years, our best clinical protocols for the treatment and diagnosis of retroperitoneal mesothelioma have not been proven and the diagnosis and treatment are challenging. PATIENT CONCERNS: A 37-year-old Chinese woman complained of bilateral low back pain for a month, with obvious symptoms of low back pain on the left side. To treat low back pain, retroperitoneal masses were found during physical examination. The patient consulted a urological specialist for further treatment. DIAGNOSIS: After the operation, pathological biopsy confirmed retroperitoneal epithelioid diffuse mesothelioma. INTERVENTIONS: After exclusion of surgical contraindications, the patient underwent laparoscopic retroperitoneal lesion resection under tracheal intubation and general anesthesia, and the operation was successful. OUTCOMES: On the tenth day after surgery, the patient vital signs were stable, and he was discharged. LESSONS: Patients with malignant peritoneal mesothelioma may have no typical clinical symptoms, and the diagnosis is based on pathological and immunohistochemical examination. In selected patients, surgical cell reduction and intraoperative intraperitoneal heat chemotherapy have become the first choice of treatment, which can achieve ideal therapeutic effects and prolong survival.

Cytological Features of Fibrin-associated Diffuse Large B-cell Lymphoma Arising in Retroperitoneal Pseudocyst: The First Case Report.

BACKGROUND/AIM: Fibrin-associated diffuse large B-cell lymphoma (FA-DLBCL) is frequently associated with the Epstein-Barr virus (EBV) and manifests as non-mass-forming microscopic lesions within fibrin-rich lesions. Herein, we describe the cytological features of FA-DLBCL. CASE REPORT: A 72-year-old man presented with a large retroperitoneal cystic mass that was treated by cyst aspiration and laparoscopic excision. Individually dispersed large, atypical cells in a necrotic background contained scant cytoplasm and hyperchromatic nuclei with irregular nuclear contours, frequent karyorrhectic debris, and mitotic figures. A fibrinous exudate with necrotic material attached to the inner surface of the cystic mass contained large, atypical cells that were individually scattered or arranged in small clusters. These were positive for cluster of differentiation 20 and Epstein-Barr virus-encoded RNA in situ hybridization. CONCLUSION: We cytologically characterized FA-DLBCL as large, atypical cells that were individually scattered or arranged in small clusters in a necrotic background. To the best of our knowledge, we revealed the cytological features of FA-DLBCL.

Open versus robot-assisted retroperitoneal tumors resection involving inferior vena cava, abdominal aorta, and renal hilum: a comparative study.

INTRODUCTION: Surgery is currently the only effective treatment for retroperitoneal tumors that do not involve any specific organ. The use of robots for removing both benign and malignant retroperitoneal tumors is considered safe and feasible. However, there is insufficient evidence to determine whether robotic retroperitoneal tumor resection (RMBRs) is superior to open retroperitoneal malignant resection (OMBRs). This study compares the short-term outcomes of robotic excision of benign and malignant retroperitoneal tumors with open excision of the same-sized tumors. METHODS: The study compared demographics and outcomes of patients who underwent robotic resection (n = 54) vs open resection (n = 54) of retroperitoneal tumors between March 2018 and December 2022. A 1:1 matching analysis was conducted to ensure a fair comparison. RESULTS: The study found that RBMRs resulted in reduced operative time (OT), estimated blood loss (EBM), and postoperative hospital stay (PSH) when compared to OBMRs. Additionally, RBMRs reduced EBL, PHS, and OT for patients with malignant tumor involvement in major vessels. No significant differences were found in tumor size, blood transfusion rate, and morbidity rate between the RBMRs and OBMRs groups. CONCLUSION: When comparing RMBRs to OMBRs, it was observed that RMBR was associated with lower (EBL), shorter postoperative hospital stays (PHS), and reduced operative time (OT) in a specific group of patients with both benign and malignant tumors.

What is the association of preoperative biopsy with recurrence and survival in retroperitoneal sarcoma? A systematic review by the Australia and New Zealand Sarcoma Association clinical practice guidelines working party.

Preoperative biopsy for retroperitoneal sarcoma (RPS) enables appropriate multidisciplinary treatment planning. A systematic review of literature from 1990 to June 2022 was conducted using the population, intervention, comparison and outcome model to evaluate the local recurrence and overall survival of preoperative biopsy compared to those that had not. Of 3192 studies screened, five retrospective cohort studies were identified. Three reported on biopsy needle tract seeding, with only one study reporting biopsy site recurrence of 2 %. Two found no significant difference in local recurrence and one found higher 5-year local recurrence rates in those who had not been biopsied. Three studies reported overall survival, including one with propensity matching, did not show a difference in overall survival. In conclusion, preoperative core needle biopsy of RPS is not associated with increased local recurrence or adverse survival outcomes.

A retrospective clinical analysis of 11 cases of PEComa from different sites.

PURPOSE: The objective of this paper is to offer a thorough examination of the clinical presentations, etiology, and treatment strategies associated with perivascular epithelioid cell tumors (PEComas). METHODS: This retrospective study examined the comprehensive archival data of PEComa cases diagnosed at Beijing Hospital from 2015 to 2023. The pathology slides of all patients were thoroughly reassessed by two experienced pathologists. A thorough retrospective analysis was undertaken, incorporating clinicopathological data including gender, age at diagnosis, initial clinical manifestations, signs, disease onset site, tumor markers, imaging findings, therapeutic modalities, pathological features, immunohistochemical profiles, treatment responses, and prognostic indicators. Patients were evaluated for disease severity according to established pathological classification criteria and were followed up until the designated analysis cut-off date. In instances where patients were unable to be monitored on-site, they were contacted via telephone for postoperative follow-up inquiries. RESULTS: This study included 11 patients with ages ranging from 17 to 66 years old, presenting with the disease in multiple anatomical sites, including the retroperitoneum (2/11), liver (4/11), kidney (4/11), lung (1/11), and broad ligament of the uterus (1/11). Most patients presented with non-specific clinical symptoms and were subsequently diagnosed with space-occupying lesions upon physical examination. The tumor demonstrated progressive growth and enlargement, which could result in compression of neighboring organs. Preoperative imaging alone is insufficient for a definitive diagnosis of PEComa, but MRI can provide an initial evaluation of the tumor's potential malignancy. Molecular marker testing specific to PEComa, such as HMB-45 (90.0%), SMA (81.8%), Melan-A (90.9%), vimentin (90.9%), and Desmin (36.3%), was conducted on all patients. No adjuvant therapies were administered postoperatively. Upon analysis, no instances of relapse at the primary site or the development of new tumors at other sites were observed. Regular imaging reviews of three patients with malignant PEComa post-surgery showed no evidence of recurrence. CONCLUSIONS: The clinical presentation, tumor biomarkers, and imaging characteristics of PEComa lack specificity, necessitating dependence on pathology and immunohistochemistry for precise diagnosis. The mainstay of treatment consists of surgical resection, with patients typically experiencing a favorable prognosis.

Metastasis-directed therapy in testicular cancer.

PURPOSE OF REVIEW: This review highlights the importance of addressing testicular cancer metastasizing beyond the retroperitoneum, focusing on multidisciplinary approaches and advances in treatment. RECENT FINDINGS: Recent literature emphasizes on the evolving landscape of metastasis-directed therapy, including surgical interventions, chemotherapy regimens, and radiation therapy. The effectiveness of these treatments varies depending on the site of metastasis, with various approaches improving survival rates and quality of life for patients. We divide our review in an organ-specific manner and focus on chemotherapeutic, surgical, and radiation therapy approaches pertaining to each site of metastasis. SUMMARY: Our review suggests the pressing need for continued research to refine and personalize treatment strategies. These efforts are important for enhancing clinical practice, ultimately leading to better outcomes for patients with metastatic testicular cancer.

Intense FDG Uptake in Well-Differentiated Inflammatory Liposarcoma of the Retroperitoneum.

ABSTRACT: Inflammatory variant of well-differentiated liposarcoma is a rare subtype of liposarcoma, and its imaging features have been rarely reported. We describe FDG PET/CT findings in a case of well-differentiated inflammatory liposarcoma. The tumor showed no detectable fat and intense FDG uptake and caused diffuse FDG uptake of the bone marrow due to paraneoplastic leukemoid reaction. Microscopically, there were extensive inflammatory infiltrates in the tumor, which may contribute to the intense FDG uptake. This case indicates that although well-differentiated liposarcoma usually shows low-grade FDG uptake, inflammatory variant of well-differentiated liposarcoma can show intense FDG uptake mimicking high-grade liposarcoma.

Progress in Retroperitoneal Sarcoma Management: Surgical and Radiotherapy Approaches.

Surgical resection is the cornerstone of curative treatment for retroperitoneal sarcomas (RPS), aiming for complete excision, yet the complexity of RPS with its proximity to vital structures continues to lead to high local recurrence rates after surgery alone. Thus, the role of radiotherapy (RT) continues to be refined to improve local control, which remains an important goal to prevent RPS recurrence. The recently completed global randomized trial to evaluate the role of surgery with and without preoperative RT - STRASS1, did not demonstrate a significant overall benefit for neoadjuvant RT based on the pre-specified definition of abdominal recurrence-free survival, however, sensitivity analysis using a standard definition of local recurrence and analysis of outcomes by compliance to the RT protocol suggests histology-specific benefit in well- and some de-differentiated liposarcomas. Ultimately, multidisciplinary collaboration and personalized approaches that consider histological sarcoma types and patient-specific factors are imperative for optimizing the therapeutic strategy in the management of RPS.

Recurrence of locally invasive retroperitoneal dedifferentiated liposarcoma shortly after surgery: A case report and literature review.

RATIONALE: Retroperitoneal dedifferentiated liposarcoma (RPDDL) is an uncommon malignancy, which often remains undetected for many years due to having adequate space in the retroperitoneal cavity and lacking clinical manifestations in the early stage of the disease. Surgical procedure is usually used as the first choice for treatment. However, it is prone to local recurrence after the operation, resulting in an unfavorable prognosis. Our aim is to draw useful lessons from the new case and provide some experience for management of the disease. PATIENT CONCERNS: We describe a 55-year-old male patient who was admitted for a 3-week history of persistent dull ache of the left waist. A large mass of the left upper abdomen was palpated in physical examination. Moreover, the imaging examination revealed that the diameter of the mass was about 21 cm, and some adjacent vital organs were invaded, which brought great challenges to complete surgical resection. DIAGNOSIS: The postoperative pathological results confirmed that the mass was RPDDL with invasion of the surrounding vital structures including pancreas, spleen, left adrenal gland, left kidney, and vasculature with tumor emboli. INTERVENTIONS: Surgical resection of the mass was performed by our multidisciplinary team. The patient received chemotherapy 1 month after surgery. OUTCOMES: The effect of chemotherapy seemed to be unsatisfactory. Local multifocal recurrence of the tumor was considered about 2 months after surgery. Finally, he gave up any treatments and died of the disease. LESSONS: Regular physical examination and ultrasound screening may detect the disease as early as possible, especially for high-risk group aged 60 to 70, which should be popularized. Incomplete resection, vascular invasion, and interruption of postoperative treatment may lead to an unfavorable prognosis. Therefore, we think that patients with the disease may benefit from complete surgical resection and uninterrupted adjuvant therapy.

[Advances in the etiology of retroperitoneal liposarcoma].

Retroperitoneal liposarcoma is the most common retroperitoneal soft tissue tumor with insidious onset, difficulty in treatment, and easy recurrence. Different subtypes of retroperitoneal liposarcoma differ significantly in pathogenic mechanism, biological behavior, and prognosis. The characteristic molecular event of well-differentiated and dedifferentiated liposarcoma is the amplification of the long arm segment of chromosome 12. The genome of myxoid liposarcoma is characterized by translocations of chromosomes 12 and 16 to form fusion genes. The genomic changes of pleomorphic and myxoid pleomorphic liposarcoma are complex, with multiple chromosomal structural abnormalities. Several signaling pathways related to adipocyte differentiation or lipid metabolism have been found to be involved in the initiation and progression of retroperitoneal liposarcoma. It is unclear whether retroperitoneal liposarcoma originates from naive preadipocytes or dedifferentiated mature adipocytes, and its metabolic characteristics are also poorly understood. The first-line drug treatment for retroperitoneal liposarcoma is anthracycline-based chemotherapy, but patients receive little benefit. Therefore, it is urgent to strengthen the basic research on retroperitoneal liposarcoma to find effective therapeutic targets.

Clinical outcomes after inferior vena cava resection for malignant disease. A single center experience of 51 vena cava resections.

BACKGROUND AND OBJECTIVE: For tumors involving inferior vena cava (IVC), surgery with complete resection remains the first line treatment. Management of IVC after resection, either ligation without reconstruction or primary reconstruction, is debated. Our study aimed to evaluate type of venous reconstruction, anticoagulation management and morbidity. METHODS: A French single center database of patients who underwent partial or total circumferencial resection of the IVC for malignant disease was analyzed. Inclusion criteria were any oncologic procedure for a retroperitoneal neoplasm requiring concomitant resection of the IVC with or without venous reconstruction with prosthesis. Exclusion criteria were surgery before year 2000. Data were descriptive and reverse Kaplan Meier was used for follow-up calculation. The endpoints were the rate of prosthetic reconstruction, the use of anticoagulation and the post-operative outcomes. RESULTS: Fifty - one patients were included with a median duration of follow-up of 54.8 months. The majority of patients were men (56.9%). Median age of the population was 44.1 years. Most of the patients underwent surgery for primary testicular cancer and for sarcoma. Complete IVC resections were performed in 46 (90,2%) patients, 32 having a concomitant prosthetic replacement. Eight patients underwent aortic resection in the same operative time. Postoperative morbidity was 33.3%. Post-operative anticoagulation was done in 24 patients. At 1 month, four patients developed thrombosis in the prosthesis. CONCLUSIONS: IVC resections are feasible and safe. Venous reconstruction and postoperative management were planned according to the preoperative imaging and intraoperative findings. We propose a decision-tree for peri-operative management and anticoagulation.