Retroperitoneal Sarcomas: An Update on the Diagnostic Pathology Approach

Whole Abdominal Radiotherapy Is Tolerable and Effective in Children and Young Adults With Intra-Abdominal Sarcoma: A Canadian Sarcoma Research and Clinical Collaboration (CanSaRCC) Study

BACKGROUND

Whole abdominal radiotherapy (WART) is utilized in children, adolescents, and young adults with intra-abdominal sarcoma, but efficacy and toxicity are uncertain.

METHODS

Sarcoma patients diagnosed at ≤39 years of age between 1998 and 2023 who received WART were identified from a national registry. Patient and tumor characteristics, treatment, response, and survival outcomes were assessed.

RESULTS

Twenty patients with desmoplastic small round cell tumor (DSRCT) (n = 7), rhabdomyosarcoma (RMS) (n = 6), Ewing sarcoma, rhabdoid tumor, endometrial stromal tumor (each n = 1), and sarcoma not-otherwise-specified (NOS) (n = 4) were included. Among 17 patients who received WART as part of upfront therapy, 16 had abdominal metastatic disease (94.1%) (peritoneal deposits n = 9, malignant ascites n = 8 [including two with both peritoneal deposits and malignant ascites] and liver metastases n = 1), while one was initially localized. Median WART dose was 22.5 Gy (range: 10.5-30); median kidney and liver doses were 14.9 Gy (range: 7.7-20.7) and 21.0 Gy (range: 13.1-27.7), respectively. Three patients developed Grade 3 acute toxicity; diarrhea (n = 2) or elevated creatinine (n = 1); two RMS patients developed second malignancies. Two-year overall and progression-free survival estimates were 100% and 80% (95% confidence interval [CI]: 51.6%-100%) in RMS; 62.5% (95% CI: 32%-100%) and 50% (95% CI: 22.5%-100%) in DSRCT. Five-year cumulative incidence of abdominal recurrence was 33.3% (95% CI: 11.4%-57.3%) with WART failure in DSRCT (n = 2) and sarcoma NOS (n = 1). Three patients received WART following relapse; all recurred; two within the WART field.

CONCLUSIONS

WART is well tolerated among young sarcoma patients and provides meaningful local disease control when utilized in front-line adjuvant therapy.

A rare case of abdominal (lesser sac) myxoid liposarcoma: A case report

BACKGROUND AND IMPORTANCE

Myxoid liposarcomas (MLS) are genetically defined by DDIT3 gene fusions and most commonly arise in the extremities. They can also occur in the retroperitoneum as a primary site. However, there are controversies in its occurrence. It peaks in the fourth and fifth decades of life, affecting both gender equally.

CASE PRESENTATION

A 38-year-old male patient presented with painless abdominal swelling, indigestion, and loss of appetite of 08 months duration. The abdominal examination showed a regular non-tender mass filling the left upper quadrant mimicking huge splenomegaly. An abdominopelvic ultrasound shows a huge echo complex mass filling the left upper abdomen. A contrast CT scan revealed a well-defined mass filling the lesser sac with a moderate mass effect on nearby abdominal organs with a clear fat plane and hence with no sign of invasion. Laboratory tests were found to be in the normal range except moderate anemia. Laparotomy was decided after case analysis and correction of anemia. A huge mass excised from the lesser sac and sent for histology. The patient went home on the third day after laparotomy. Histopathologic results reported retroperitoneal MLS with the classic microscopic findings.

CLINICAL DISCUSSION

MLS is the second most common type of liposarcoma, and tends to occur in the lower extremities. It rarely occurs in the retroperitoneum, with most cases being classified as atypical lipomatous tumors with prominent myxoid change.

CONCLUSION

It is crucial to differentiate a metastatic MLS originating from the lower extremities. The principle of treatment is complete surgical resection.

Primary Mesenteric Well-Differentiated Inflammatory Liposarcoma With Mucosal Extension: A Lesion With High Risk for Misdiagnosis

Well-differentiated liposarcomas are common retroperitoneal lesions, but exceedingly rare when primary to the small bowel mesentery, with only a handful of cases reported in the literature. Presented is a patient with a primary mesenteric well-differentiated inflammatory liposarcoma with mucosal extension at high risk for misdiagnosis. A broad differential diagnosis with careful histopathologic observation, ancillary immunohistochemical studies, and fluorescent in situ hybridization for MDM2 amplification are key to make a correct diagnosis. This is especially true if such a lesion was first noted in the lamina propria on histopathology from an endoscopic mucosal biopsy.

Diagnostic challenges of retroperitoneal leiomyosarcoma: A case of confusion with adrenal tumour

Leiomyosarcoma (LMS) represents an aggressive neoplasm that often involves a diagnostic challenge when encountered in atypical anatomical sites. The case here exposed involves a 70-year-old female with a retroperitoneal mass measuring 65mm×65mm, likely of adrenal origin, warranting consideration for adrenalectomy. Histopathological examination reveals spindle cells arranged in intersecting fascicles, displaying pleomorphism and necrosis, and is immunohistochemically positive for actin and desmin markers. The definitive diagnosis is LMS, demonstrating venous origin without infiltration of the adrenal gland. Regrettably, the patient succumbed to post-operative complications. The inconspicuous nature of LMS in this anatomical niche complicates preclinical detection, underscoring the pivotal role of histopathological analysis in its identification. Furthermore, achieving complete excision proves challenging, resulting in a poorer prognosis compared to conventional LMS, despite the availability of alternative treatment modalities. Given the absence of standardized management protocols, a multidisciplinary approach remains essential.

Dedifferentiated liposarcoma with extensive cystic change causing significant diagnostic challenges: report of two cases and review of the literature

BACKGROUND

Retroperitoneal dedifferentiated liposarcoma is a rare, aggressive malignancy, characterized by high rates of recurrences and the potential for metastasis. On imaging, these tumors typically present as a solid mass with lipomatous and non-lipomatous components. Cystic changes of dedifferentiated liposarcomas is exceedingly rare and might pose significant diagnostic challenges, with only a few cases reported in the literature. REPORT OF 2 CASES: We here present two cases of retroperitoneal dedifferentiated liposarcoma with a rare cystic presentation in two female patients aged 51 and 62 years. Imaging revealed large perinephric cystic masses measuring up to 13.0 cm and 16.1 cm, respectively, with calcifications of the cyst wall observed in the second case. Differential diagnoses included cystic echinococcosis, mesenchymal neoplasms, and benign cystic lesions (e.g. endometrial cyst). Both patients underwent upfront compartmental en-bloc surgical resection of the tumor mass and the kidney after multidisciplinary tumor board (MDT) discussion. Macroscopically, the tumors were adherent to but sharply demarcated from the kidney. Histological examination of the first case revealed a small component of well-differentiated liposarcoma (WDLPS) adjacent to a large non-lipogenic sarcoma with a prominent whirling pattern, compatible with dedifferentiation. The second case demonstrated a spindle cell neoplasm with prominent osteosarcomatous heterologous differentiation. MDM2 amplification was confirmed in both cases by molecular testing. No long-term follow-up data is available for either patient.

CONCLUSION

In conclusion, these cases highlight the importance of recognizing unusual and extensive cystic changes of dedifferentiated liposarcoma, which can complicate the diagnostic work-up.

Retroperitoneal leiomyosarcoma diagnosis and management in a chronic kidney disease context: A case report

INTRODUCTION AND IMPORTANCE

While the treatment approach for sarcomas seems straightforward and well-defined, we often encounter several diagnostic or therapeutic challenges in clinical practice. This article presents a case of retroperitoneal leiomyosarcoma in a patient with chronic kidney disease, highlighting the complexity of managing such cases.

CASE REPORT

A 63-year-old woman with a history of chronic kidney disease presented with a progressively enlarging mass in her right flank. A CT scan revealed a retroperitoneal mass affecting the muscular layer of the right lumbar ureter, without invading the kidney. Percutaneous biopsies concluded to a smooth muscle tumor with positive anti-caldesmone and anti-desmin antibodies. A 99 m Tc DMSA renal revealed significant impairment of the right kidney function while the left kidney function remained normal. The surgical procedure involved removing the mass, as well as the right kidney and ureter. Histopathological examination confirmed the diagnosis of leiomyosarcoma. No locoregional recurrence or metastases were noted after a 13-month follow-up.

DISCUSSION

Leiomyosarcomas are malignant tumors that can affect various organs, with retroperitoneum being the second most common location. A CT scan and abdominal MRI are standard imaging technique to evaluate this disease. Percutaneous biopsy and pathology are performed to confirm the nature of the tumor, especially when neoadjuvant treatment is necessary for metastatic tumors. Compartmental resection with clear margins is the only potential curative treatment. Even after R0 resection the risk of recurrence varies between 20 and 75 %.

CONCLUSION

Managing retroperitoneal leiomyosarcoma, especially in patients with comorbidities like chronic kidney disease, necessitates a multidisciplinary approach.

CT and MR imaging of a huge retroperitoneal synovial sarcoma: A case report

Retroperitoneal synovial sarcoma is extremely rare, with only a few cases reported in the literature. The diagnosis is often made late, due to anatomical considerations, with common symptoms including low back pain and weight loss. Imaging is critical for diagnosis, often revealing a heterogenous mass with the "triple sign" and calcifications. The main differential diagnoses include liposarcoma, undifferentiated pleomorphic sarcoma and leiomyosarcoma. Surgical resection remains the treatment of choice, though it is not always feasible, which contributes to the poor prognosis. The presented case is a retroperitoneal synovial sarcoma in a 29 years old man with findings from ultrasound, computed tomography and magnetic resonance imaging.

Retroperitoneal Sarcomatoid Yolk Sac Tumor in a Chemotherapy-Naive Patient With Testicular Postpubertal Type Teratoma: A Rare Case Report With Emphasis on Molecular Features

Sarcomatoid yolk sac tumor is a very rare histologic type of testicular germ cell tumor and is mainly reported in testicular germ cell tumor patients who receive chemotherapy. Herein, we report an extremely rare concurrent retroperitoneal sarcomatoid yolk sac tumor in a man with a testicular postpuberal teratoma before he received chemotherapy. A 37-year-old man initially presented with a persistent abdominal pain. Subsequent imaging studies revealed a 9.6-cm retroperitoneal mass, and 2 testicular masses (3.1 cm and 0.9 cm in greatest dimension, respectively). His serum tumor markers were within normal ranges. His radical orchiectomy demonstrated a postpubertal type teratoma with an adjacent scarring nodule. Later, his retroperitoneal tumor showed spindle tumor cells embedded in predominantly myxoid and focally fibrous stroma with diffuse and strong immunoreactivity for keratin AE1/AE3, SALL4 and glypican 3. No tumor necrosis or brisk mitotic figures were observed. A diagnosis of sarcomatoid yolk sac tumor was rendered. Fluorescence in situ hybridization analysis of his retroperitoneal sarcomatoid yolk sac tumor revealed polysomy 12 and MYC amplification, whereas no evidence of isochromosome 12p [i(12p)], and DNA sequencing showed 6 mutations per megabase (muts/Mb), and the somatic alterations included ARAF amplification and ATR I774Yfs*5. Considering its rarity, sarcomatoid yolk sac tumor may pose diagnostic challenges. Therefore, relevant clinicoradiologic information and ancillary work up, including immunohistochemistry and molecular studies, may be helpful for the accurate classification. Our tumor further raises awareness of this rare event, expands the spectrum of its clinical presentation, and explores the molecular features.

Lipoleiomyosarcoma Presenting as Massive Retroperitoneal Mass: An Unusual Soft Tissue Tumor of Abdomen and its Review of Literature

Lipoleiomyosarcoma is a malignant tumor of both mesenchymal and smooth muscle origin. Lipoleiomyosarcoma is a very rare type of retroperitoneal sarcoma, which by itself is a rare type of soft tissue sarcoma. Lipoleiomyosarcoma is a very rare subtype of liposarcoma, which is the most common type of retroperitoneal sarcoma. To our best review of available literature, this was the first case of lipoleiomyosarcoma presenting as a massive retroperitoneal mass of size 50 × 50 × 30 cm, managed with multi-visceral R0 resection. The computed tomography of the abdomen showed a massive fat density lesion with internal soft density lesions and internal calcifications. Multivisceral resection was planned and executed and achieved R0 resection. We suggest that lipoleiomyosarcoma should be included in differential diagnosis of retroperitoneal tumors, and multi-visceral R0 resection should be considered as an option for lipoleiomyosarcoma, as these tumors have very good prognosis with R0 resection.

An infrequent case of retroperitoneal synovial sarcoma

Synovial sarcoma (SS) is an uncommon malignant tumor, ranking third in prevalence within the soft tissue sarcomas group. The vast majority of synovial sarcomas are present in the extremities, with only 15% developing in the retroperitoneal space. Retroperitoneal synovial sarcoma (RSS) is an infrequent case of SS, with only about 20 cases reported in the literature. Diagnosing RSS before treatment remains challenging because of its nonspecific clinical symptoms. The disease is often detected at a later stage, leading to additional damage to other organs as well as complicated and ineffective treatment. Consequently, the 5-year survival rate is only 20%-29%. This report introduces a case of RSS in a 19-year-old male patient with imaging characteristics on computed tomography (CT) and magnetic resonance (MR).

Surgical management of giant retroperitoneal liposarcoma: Case report

Tumors originating from soft tissues are uncommon, among these tumors, liposarcomas are the most frequent. These tumors remain asymptomatic for a long time, and only revealing themselves when they reach an important size. In such cases, treatment is difficult, requiring extensive surgery procedures that can excise several adjacent structures, potentially completed by adjuvant radiotherapy. Despite successful treatment, the recurrence rate remains very high. We report the case of a giant liposarcoma requiring a monobloc extensive resection involving the removal of the tumor, left kidney, left adrenal gland, and a portion of the posterior abdominal wall.

Advancements in Diagnosis and Multimodal Treatment Strategies for Retroperitoneal Tumors: A Comprehensive Review

Retroperitoneal tumors (RPTs) encompass both benign and malignant entities, constituting ~0.1% to 0.2% of all malignant tumors, of which 70% to 80% manifest malignancy. Predominantly, retroperitoneal sarcomas (RPS) represent the most prevalent subtype among RPT. With over 70 histologic forms identified, liposarcomas and leiomyosarcomas emerge as the primary constituents of RPS. Accurate diagnosis of RPTs necessitates preoperative core-needle biopsy and comprehensive imaging assessment. The current staging protocol for RPS relies on the eighth edition of the American Joint Committee on Cancer/TNM classification. Surgical excision remains the established gold standard for treating RPS. Therapeutic approaches vary according to the underlying pathophysiology. Although chemotherapy and radiotherapy exhibit efficacy in managing metastatic and recurrent unresectable RPS, their role in primary RPS remains unresolved, necessitating further clinical trials for validation. Concurrently, ongoing research explores the potential of targeted therapies and immunotherapy. This literature review aims to provide a comprehensive overview of existing research, delineating diagnostic pathways and optimal therapeutic strategies for RPT.

Rapid and Precise Diagnosis of Retroperitoneal Liposarcoma with Deep-Learned Label-Free Molecular Microscopy

The retroperitoneal liposarcoma (RLPS) is a rare malignancy whose only curative therapy is surgical resection. However, well-differentiated liposarcomas (WDLPSs), one of its most common types, can hardly be distinguished from normal fat during operation without an effective margin assessment method, jeopardizing the prognosis severely with a high recurrence risk. Here, we combined dual label-free nonlinear optical modalities, stimulated Raman scattering (SRS) microscopy and second harmonic generation (SHG) microscopy, to image two predominant tissue biomolecules, lipids and collagen fibers, in 35 RLPSs and 34 normal fat samples collected from 35 patients. The produced dual-modal tissue images were used for RLPS diagnosis based on deep learning. Dramatically decreasing lipids and increasing collagen fibers during tumor progression were reflected. A ResNeXt101-based model achieved 94.7% overall accuracy and 0.987 mean area under the ROC curve (AUC) in differentiating among normal fat, WDLPSs, and dedifferentiated liposarcomas (DDLPSs). In particular, WDLPSs were detected with 94.1% precision and 84.6% sensitivity superior to existing methods. The ablation experiment showed that such performance was attributed to both SRS and SHG microscopies, which increased the sensitivity of recognizing WDLPS by 16.0 and 3.6%, respectively. Furthermore, we utilized this model on RLPS margins to identify the tumor infiltration. Our method holds great potential for accurate intraoperative liposarcoma detection.

Survival Outcome of Retroperitoneal Sarcomas Treated With a Surgery-First Approach: A Single-Center Experience

Background Retroperitoneal sarcomas (RPS) are rare and complex tumors originating from the retroperitoneal space, an anatomical region nestled behind the abdominal cavity and shielded by the posterior abdominal wall. Late clinical presentation is a hallmark of retroperitoneal sarcomas. The symptoms are often nonspecific, and nodal metastases are rare. Computed tomography (CT) remains the investigation of choice, and a preoperative biopsy is usually not needed. Surgical resection remains the mainstay of treatment, along with adjuvant radiation and chemotherapy. Survival rates are in general poor, even after complete resection. In this study, we attempt to shed some light on the clinicopathological profiling of retroperitoneal sarcomas and their survival outcomes. Objective The objective of this study is to assess the demographic, clinical, and pathological profiling of patients with retroperitoneal sarcoma and to study the survival of patients with retroperitoneal sarcoma. Methodology We conducted a hospital-based retrospective observational study in a tertiary care center in South India between January 2011 and January 2021. We included all patients with histopathologically proven retroperitoneal sarcoma. Metastatic cases and those who underwent chemotherapy or radiation prior to presentation were excluded. Their demographics, pathological reports, and survival were followed up and collected, and statistical analysis was done. Results The study included 16 cases with retroperitoneal sarcomas across the decade in which the data was collected, confirming the rarity of the tumor, out of which more than 40% of patients were above the age of 60. The most common symptom was found to be a bloating sensation in nine patients, followed by abdominal pain in three patients. Seventy-five percent of the patients were found to have a T4 (i.e., a size of more than 15 cm) tumor at presentation. Well-differentiated liposarcoma was found to be the most common pathological variant accounting for 25% of the cases. The mean survival was found to be 8.05 years, which dropped to 5.74 years in Grade 3 tumors. Conclusion Retroperitoneal sarcomas are rare tumors of which liposarcoma is the most common variant. A significant reduction in the mean survival was identified in Grade 3 sarcomas compared to the cumulative survival time of Grade 1 and Grade 2 retroperitoneal sarcomas.

Organ Infiltration and Patient Risk After Multivisceral Surgery for Primary Retroperitoneal Liposarcomas

BACKGROUND

The extent of histological organ involvement (HOI) to organs and structures of a retroperitoneal liposarcoma may have prognostic implications. This study investigated incidence, characteristics, and risk association of HOI in these patients.

PATIENTS AND METHODS

Data of patients who underwent multivisceral resection for primary liposarcoma (2009-2014) were retrospectively analyzed. HOI was the variable of interest and was classified into four degrees: absent (HOI-0), perivisceral (HOI-1), initial (HOI-2), and advanced (HOI-3). Primary endpoint was overall survival (OS). Secondary endpoint was disease-free survival (DFS). The prognostic value of HOI was adjusted for preoperative treatment and the Sarculator nomogram score.

RESULTS

A total of 109 patients were included. HOI-0, HOI-1, HOI-2, and HOI-3 were detected in 9 (8.3%), 11 (10.1%), 43 (39.4%), and 46 (42.2%) patients. Median follow-up was 8.4 years [interquartile range (IQR) 7.2-9.6 years]. There were 68 recurrences and 50 patient deaths observed, resulting in a 10-year OS and DFS of 51.1% [95% confidence interval (CI) 41.9-62.1%] and 34.1% (95% CI 25.2-46.1%), respectively. Clinically relevant HOIs (HOI-2 and HOI-3) were found in 35/45 (77.8%) and 54/64 (84.4%) cases of well- and de-differentiated liposarcomas, respectively. On multivariable survival analysis, patients with HOI-3 had significantly shorter OS (HOI-3 vs HOI-0/HOI-1 HR 2.92; p = 0.012) and DFS (HOI-3 vs HOI-0/HOI-1 HR 2.23; p = 0.045), independently of the nomogram score (OS: HR 2.93; p < 0.001; DFS: HR 1.78; p = 0.003).

CONCLUSIONS

Initial and advanced HOIs are frequently detected in both well-differentiated and de-differentiated liposarcomas, supporting that multivisceral resection may be needed. HOI stratifies the risk of patients with primary retroperitoneal liposarcoma.

Practical Management of Adult Ultra-Rare Primary Retroperitoneal Soft Tissue Sarcoma: A Focus on Perivascular Epithelioid Tumours and Extraosseous Ewing Sarcoma

With the exception of well-differentiated liposarcoma, dedifferentiated liposarcoma, leiomyosarcoma, solitary fibrous tumour, malignant peripheral nerve sheath tumour, and undifferentiated pleomorphic sarcoma, the majority of the ≈70 histologic subtypes of retroperitoneal sarcoma are defined as 'ultra-rare' sarcomas, with an incidence of ≤1-5/1,000,000 persons/year. For most of these ultra-rare RPS subtypes, diagnosis and treatment follows international guidelines for the management of more common RPS histologies, with en bloc surgical resection as the mainstay of curative treatment, and enrolment in clinical trials where possible. Because the treatment of RPS is heavily driven by histology, the surgeon must be familiar with specific issues related to the diagnosis and management of ultra-rare sarcoma subtypes. Expert radiological and surgeon reviews are required to differentiate similarly presenting tumours where surgery can be avoided (e.g., angiomyolipoma), or where upfront systemic therapy is indicated (e.g., extraosseous Ewing's sarcoma). Thus, the management of all retroperitoneal sarcomas should occur at a sarcoma referral centre, with a multidisciplinary team of experts dedicated to the surgical and medical management of these rare tumours. In this focused review, we highlight how diagnosis and management of the ultra-rare primary RPS histologies of malignant perivascular epithelioid cell tumour (PEComa), extraosseous Ewing sarcoma (EES), extraosseous osteosarcoma (EOS), and rhabdomyosarcoma (RMS) critically diverge from the management of more common RPS subtypes.

Updated Review and Clinical Recommendations for the Diagnosis and Treatment of Patients with Retroperitoneal Sarcoma by the Spanish Sarcoma Research Group (GEIS)

Soft tissue sarcomas (STS) are an uncommon and biologically heterogeneous group of tumors arising from mesenchymal cells. The incidence is estimated at five cases per 100,000 people per year. Retroperitoneal sarcomas (RPS) account for 10-15% of all STS, and their management depends on their anatomical characteristics and histotype. Due to their very low incidence, it is recommended that RPS be treated in reference centers and evaluated by an experienced multidisciplinary team (MDT). In Spain, the Spanish Group for Research in Sarcomas (GEIS) brings together experts from various specialties to promote research on sarcomas and improve treatment results. This paper summarizes the GEIS recommendations for the diagnosis, treatment, and follow-up of patients with RPS.

Management of Recurrent Retroperitoneal Sarcoma

Recurrence after resection of retroperitoneal sarcoma is common and varies by histological subtype. Pattern of recurrence is similarly affected by histology (e.g., well-differentiated liposarcoma is more likely to recur locoregionally, whereas leiomyosarcoma is more likely to develop distant metastases). Radiotherapy may provide effective locoregional control in limited circumstances and the data on the impact of chemotherapy are scant. Surgery for locally recurrent disease is associated with the greatest survival benefit; however, data are retrospective and from a highly selected subgroup of patients. Limited retrospective data have also suggested a survival association with the resection of limited distant metastases. Given the complexity of these patients, multidisciplinary evaluation at a high-volume sarcoma center is critical.

Updates in Pathology for Retroperitoneal Soft Tissue Sarcoma

Retroperitoneal tumors are extremely rare. More than 70% of primary retroperitoneal soft tissue tumors are malignant. The most common sarcomas in the retroperitoneum include liposarcomas and leiomyosarcoma, however other sarcomas, along with benign mesenchymal tumors, can occur. Sarcomas are a heterogenous group of tumors with overlapping microscopic features, posing a diagnostic challenge for the pathologist. Correct tumor classification has become important for prognostication and the evolving targeted therapies for sarcoma subtypes. In this review, the pathology of retroperitoneal soft tissue sarcomas is discussed, which is important to the surgical oncologist. In addition, less common sarcomas and benign mesenchymal tumors of the retroperitoneum, which may mimic sarcoma clinically and pathologically, are also discussed.

Solid Primary Retroperitoneal Masses in Adults: An Imaging Approach

Mass lesions in the retroperitoneal space may be primary or secondary. Primary retroperitoneal mass lesions are relatively uncommon as compared to pathology that arises secondarily from retroperitoneal organs. These may be solid or cystic lesions. The overlapping imaging features of various solid primary retroperitoneal tumors make the diagnosis difficult, and hence, histopathology remains the mainstay of diagnosis. This paper provides a brief review of the anatomy of the retroperitoneal space and provides an algorithmic approach based on cross-sectional imaging techniques to narrow down the differential diagnosis of solid primary retroperitoneal masses encountered in the adult population.

A case report of retroperitoneal Ewing sarcoma requiring adrenalectomy

Introduction and importance

Ewing's sarcoma is a rare entity of malignant in both skeletal and extra-skeletal sites. There are few patients reported as Extra-Skeletal Sarcoma, and fewer reported cases for Extraskeletal Ewing sarcoma involving the retroperitoneal region. Reporting such a rare entity will add to literature in helping the diagnosis and management of such cases.

Case presentation

We present a case of 26 year old previously healthy female complaining of a vague abdominal pain and discovered to have retroperitoneal Ewing sarcoma adherent to left adrenal gland.

Clinical discussion

She was managed with a combination of neoadjuvant chemotherapy and resection through exploratory laparotomy.

Conclusion

In short, Ewing sarcoma should be considered in the differential diagnosis for young patient who is presenting with a retroperitoneal mass.

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Ewing's sarcoma is a rare entity of malignant in both skeletal and extra-skeletal sites.

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There are few patients reported as Extra-Skeletal Sarcoma (ESS).

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EES involving retroperitoneal region, from previous studies.

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We present a case of EES involving the retroperitoneal region and its subsequent management.

Deep Learning Networks for Automatic Retroperitoneal Sarcoma Segmentation in Computerized Tomography

The volume estimation of retroperitoneal sarcoma (RPS) is often difficult due to its huge dimensions and irregular shape; thus, it often requires manual segmentation, which is time-consuming and operator-dependent. This study aimed to evaluate two fully automated deep learning networks (ENet and ERFNet) for RPS segmentation. This retrospective study included 20 patients with RPS who received an abdominal computed tomography (CT) examination. Forty-nine CT examinations, with a total of 72 lesions, were included. Manual segmentation was performed by two radiologists in consensus, and automatic segmentation was performed using ENet and ERFNet. Significant differences between manual and automatic segmentation were tested using the analysis of variance (ANOVA). A set of performance indicators for the shape comparison (namely sensitivity), positive predictive value (PPV), dice similarity coefficient (DSC), volume overlap error (VOE), and volumetric differences (VD) were calculated. There were no significant differences found between the RPS volumes obtained using manual segmentation and ENet (p-value = 0.935), manual segmentation and ERFNet (p-value = 0.544), or ENet and ERFNet (p-value = 0.119). The sensitivity, PPV, DSC, VOE, and VD for ENet and ERFNet were 91.54% and 72.21%, 89.85% and 87.00%, 90.52% and 74.85%, 16.87% and 36.85%, and 2.11% and -14.80%, respectively. By using a dedicated GPU, ENet took around 15 s for segmentation versus 13 s for ERFNet. In the case of CPU, ENet took around 2 min versus 1 min for ERFNet. The manual approach required approximately one hour per segmentation. In conclusion, fully automatic deep learning networks are reliable methods for RPS volume assessment. ENet performs better than ERFNet for automatic segmentation, though it requires more time.

Synchronous Occurrence of Advanced Gastric Carcinoma with Retroperitoneal Liposarcoma: A Case Report

BACKGROUND Gastric carcinoma (GC) remains one of the most common and deadly neoplasms in the world. Liposarcoma (LPS) is the most common sarcoma of adults. However, synchronous or metachronous occurrence of GC with LPS seems to be very rare. Tumor staging and differential diagnosis with these cases are extremely difficult. CASE REPORT The patient was a man in his 70s, who reported anorexia and weight loss of 4 kg over 2 months. Gastroscopy demonstrated a large tumor of Borrmann type 3, of which histology was moderately to poorly differentiated adenocarcinoma. The clinical stage was initially defined as IVb due to a 11×6 cm retroperitoneal (RP) tumor. Despite chemotherapy for GC, the RP tumor rapidly enlarged. Endoscopic ultrasound-guided fine-needle aspiration biopsy showed that it was an undifferentiated sarcoma. He died of hepatorenal failure secondary to severe jaundice. The autopsy revealed a synchronous occurrence of GC and RP sarcoma. GC had no areas admixed with sarcoma. Histology of RP sarcoma showed that it mainly consisted of undifferentiated sarcoma and focally of well-differentiated LPS characterized by well-differentiated adipocytes admixed with scattered atypical stromal cells. The tumor cells in both areas were positive for MDM2 and CDK4 by immunohistochemistry. The diagnosis of the RP sarcoma was revised to dedifferentiated LPS. CONCLUSIONS There were no previous case reports of synchronous occurrence of GC with LPS in the English and Japanese literature. GC and LPS pose challenging problems in their diagnoses, staging, and treatments when they occur synchronously or metachronously.

Establishment and evaluation of retroperitoneal liposarcoma patient-derived xenograft models: an ideal model for preclinical study

Retroperitoneal liposarcoma (RLPS) is one of the most common subtypes of retroperitoneal soft tissue sarcomas. It is characterized by poor sensitivity to radiotherapy and chemotherapy and a low success rate of complete surgical resection. However, there are few reliable preclinical RLPS models for target discovery and therapy research. In this study, we aimed to establish RLPS patient-derived xenograft (PDX) models that are useful for biological research and preclinical drug trials. A total of 56 freshly resected RLPS tissues were subcutaneously transplanted into non-obese diabetic-severe combined immune deficient (NOD-SCID) mice, with subsequent xenotransplantation into second-generation mice. The tumor engraftment rate of first generation PDXs was 44.64%, and higher success rates were obtained from implantations of dedifferentiated, myxous, pleomorphic, high-grade liposarcomas and those with retroperitoneal organ infiltration. The first- and second- generation PDX models preserved the histopathological morphology, gene mutation profiles and MDM2 amplification of the primary tissues. PDX models can also provide the benefit of retaining original tumor biology and microenvironment characteristics, such as abnormal adipose differentiation, elevated Ki67 levels, high microvessel density, cancer-associated fibroblast presence, and tumor-associated macrophage infiltration. Overall survival (OS) and disease-free survival (DFS) of patients with successful first-generation PDX engraftment were significantly poorer than those with failed engraftment. Treatment with MDM2 inhibitor RG7112 significantly suppressed tumor growth of DDLPS PDX in mice. In conclusion, we successfully established RLPS PDX models that were histologically, genetically, and molecularly consistent with the original tissues. These models might provide opportunities for advancing RLPS tumor biology research, facilitating the development of novel drugs, particularly those targeting MDM2 amplification, adipose differentiation process, angiogenesis, cancer-associated fibroblasts, and so on.

Musculoskeletal Soft-Tissue Sarcoma: Quality Assessment of Initial MRI Reports Shows Frequent Deviation from ESSR Guidelines

Soft-tissue sarcomas (STS) are a rare subtype of soft-tissue mass and are frequently misinterpreted as benign lesions. Magnetic resonance imaging (MRI) is the primary recommended type of diagnostics. To assess the quality of primary radiology reports, we investigated whether recommended MRI report elements were included in compliance with European Society of Musculoskeletal Radiology (ESSR) guidelines. A total of 1107 patients were evaluated retrospectively, and 126 radiological reports on patients with malignant STS were assessed for ESSR quality criteria. One or more required sequences or planes were missing in 67% of the reports. In all 126 cases, the report recognized the mass as anomalous (100%). Sixty-eight percent of the reports mentioned signs of malignancy. The majority of reports (n = 109, 87%) articulated a suspected diagnosis, 32 of which showed a mismatch with the final diagnosis (25%). Thirty-two percent of the reports had a misinterpretation of the masses as benign. Benign misinterpretations were more common in masses smaller than 5 cm (65% vs. 27%). Thirty percent of the reports suggested tissue biopsy and 6% recommended referral to a sarcoma center. MRI reports showed frequent deviations from ESSR guidelines, and protocol guidelines were not routinely met. Deviations from standard protocol and reporting guidelines could put patients at risk for inadequate therapy.