Extraskeletal Ewing's Sarcoma Research Articles

Development and verification of prognostic nomogram for extraskeletal Ewing's sarcoma based on the SEER database

BackgroundExtraskeletal Ewing's sarcoma (EES) is a rare tumor, and there is currently no predictive model for overall survival of EES patients. This study sought to use data from the Surveillance, Epidemiology, and End Results (SEER) database to develop a clinical predictive model that could be used to assess the prognosis of EES patients. MethodsWe selected and downloaded prognostic data on 356 patients diagnosed with extraskeletal Ewing’s sarcoma based on screening criteria,These patients were distributed between 2004 and 2015. 356 patients were randomly divided into a training cohort (70%) and an internal validation cohort (30%). After univariate or multifactor Cox regression analysis, the relevant variables were screened and a nomogram was constructed. The consistency index (C-index), calibration chart and receiver operating characteristic (ROC) curve were used to evaluate the established nomogram. The clinical utility of the model was verified by clinical decision curve.Study conducted and outcomes reported according to STROBE statement. ResultsAfter multifactor regression analysis, we identified five factors that were significantly associated with EES prognosis, and subsequently established a nomogram. Verification data showed that the C-index of this nomogram was 0.829 (95% CI 0.774 -- 0.884). the AUCs of the nomogram for predicting the 3- and 5-year OS were 0.91 and 0.863. the calibration curves and Decision curve analysis showed that nomogram could predict the prognosis of EES patients. ConclusionStage, age, tumour size, chemotherapy, and surgery may be independent prognostic factors for EES. our study produced a survival nomogram that can be used to predict the prognosis of patients with EES and validated its performance, which may help clinicians evaluate the condition of patients with EES and choose personalized treatment.

Establishment and characterization of a patient-derived metastatic extraskeletal Ewing sarcoma cell line ES-ZSS-1.

The methods available for treating metastatic Ewing sarcoma (ES) are inadequate; thus, innovative therapeutic approaches need to be developed. However, the lack of clinically relevant ES models has hindered the discovery of drugs for this disease. In this study, we established and characterized a patient-derived xenograft (PDX) cell line model, which was constructed using tumor tissue from a patient with metastatic extraskeletal ES. The cells were found to recapitulate the morphological and histopathological features of the patient tumor and were designated as ES-ZSS-1. The cells harbor the characteristic EWSR1-FLI1 infusion and underwent successive passages in vitro. By performing gene expression profiling, we found that the mutation in STAG2 was the most frequent. An increase in Twist1 and epithelial-to-mesenchymal transition (EMT) was recorded. These genetic features might be relevant to metastasis and resistance to chemotherapy. To summarize, the novel patient-derived ES cell line we developed closely mimics the phenotype and genotype of patient tumors, making it a reliable tool for research on metastatic ES.

Extraskeletal Ewing Sarcoma of the Extremities and Trunk: A Retrospective Analysis of a Mono-Institutional Series

Introduction: Extraskeletal Ewing sarcoma (EEwS) is a rare malignant tumor, and current international recommendations indicate systemic and local treatment like bone Ewing sarcoma (BEwS); to the best of our knowledge, very few studies tried to explore the clinical and genetic characteristics of this tumor, and the most appropriate treatment strategy remains uncertain. Methods: We reviewed 35 EEwS cases enrolled at Rizzoli Orthopedic Institute in Bologna, Italy, between 1988–2022. We performed RNA sequencing in 18 Ewing sarcoma cases, including 12 BEwSs and 6 EEwSs. We analyzed overall survival (OS), local relapse-free survival (LRFS), and metastasis-free survival (MFS) and the risk factors associated to survival. Results: Unsupervised hierarchical clustering showed no differences in the transcriptional profile between EEwS and BEwS. Five-year OS was 67% (95% confidence interval [CI]: 47–80), 5-year LRFS was 61% (95% CI: 43–75), and 5-year MFS was 55% (95% CI: 38–70). Recurrent tumors, larger than 8 cm, and elevated lactate dehydrogenase (LDH) serum value resulted to be negative prognostic factors. Conclusions: The finding/detection of a genetic profile that is indistinguishable between EEwS and BEwS confirms the view that the two subgroups belong to the same tumor entity and supports the use of a single therapeutic approach for Ewing sarcoma, regardless of the site of origin. Statistical evaluation showed that size bigger than 8 cm, elevated LDH, and recurrent tumors had a worse prognosis, suggesting a risk-stratification method for identifying patients for specific therapy treatment. However, larger, multicenter, prospective trials are called for to validate our findings.

Soft tissue tumor imaging in adults: whole-body staging in sarcoma, non-malignant entities requiring special algorithms, pitfalls and special imaging aspects. Guidelines 2024 from the European Society of Musculoskeletal Radiology (ESSR).

The revised European Society of Musculoskeletal Radiology (ESSR) consensus guidelines on soft tissue tumor imaging represent an update of 2015 after technical advancements, further insights into specific entities, and revised World Health Organization (2020) and AJCC (2017) classifications. This second of three papers covers algorithms once histology is confirmed: (1) standardized whole-body staging, (2) special algorithms for non-malignant entities, and (3) multiplicity, genetic tumor syndromes, and pitfalls. A validated Delphi method based on peer-reviewed literature was used to derive consensus among a panel of 46 specialized musculoskeletal radiologists from 12 European countries. Statements that had undergone interdisciplinary revision were scored online by the level of agreement (0 to 10) during two iterative rounds, that could result in 'group consensus', 'group agreement', or 'lack of agreement'. The three sections contain 24 statements with comments. Group consensus was reached in 95.8% and group agreement in 4.2%. For whole-body staging, pulmonary MDCT should be performed in all high-grade sarcomas. Whole-body MRI is preferred for staging bone metastasis, with [18F]FDG-PET/CT as an alternative modality in PET-avid tumors. Patients with alveolar soft part sarcoma, clear cell sarcoma, and angiosarcoma should be screened for brain metastases. Special algorithms are recommended for entities such as rhabdomyosarcoma, extraskeletal Ewing sarcoma, myxoid liposarcoma, and neurofibromatosis type 1 associated malignant peripheral nerve sheath tumors. Satisfaction of search should be avoided in potential multiplicity. Standardized whole-body staging includes pulmonary MDCT in all high-grade sarcomas; entity-dependent modifications and specific algorithms are recommended for sarcomas and non-malignant soft tissue tumors. These updated ESSR soft tissue tumor imaging guidelines aim to provide support in decision-making, helping to avoid common pitfalls, by providing general and entity-specific algorithms, techniques, and reporting recommendations for whole-body staging in sarcoma and non-malignant soft tissue tumors. An early, accurate, diagnosis is crucial for the prognosis of patients with soft tissue tumors. These updated guidelines provide best practice expert consensus for standardized imaging algorithms, techniques, and reporting. Standardization can improve the comparability examinations and provide databases for large data analysis.

Extraskeletal Ewing Sarcoma Disguised as a Vascular Malformation.

Extraskeletal Ewing sarcoma (EES) is a rare entity, accounting for only 3% of lesions encountered in upper extremity. We present two paediatric patients, who were initially diagnosed with a vascular malformation based on clinical assessment and imaging. Final histopathology revealed Ewing sarcoma of soft tissue origin, confirmed by immunohistochemical analysis. Hand surgeons, who are routinely approached for a myriad of hand pathologies, should be wary and consider EES as a differential when treating such lesions. A multidisciplinary approach with an appropriate treatment algorithm can help in a speedy diagnosis, improving the long-term prognosis of the disease. Level of Evidence: Level V (Therapeutic).

Respiratory insufficiency after brain metastasectomy for extraskeletal Ewing sarcoma in an adult patient with mucopolysaccharidosis type II: a case report.

Mucopolysaccharidosis is a rare lysosomal storage disease caused by deficiencies in enzymes involved in the degradation of glycosaminoglycans. We report the case of an adult with mucopolysaccharidosis type II who developed respiratory insufficiency after brain metastasectomy for extraskeletal Ewing sarcoma. This report describes the case of a 35-year-old man with a mass on the left chest wall for 3months. Magnetic resonance imaging and computed tomography revealed a large mass on the chest wall. Positron emission tomography revealed multiple metastatic lesions in the lungs, ribs, and sternum. A needle biopsy specimen confirmed extraskeletal Ewing sarcoma, and the fusion gene EWS-FLI1 was positive. Subsequently, multidrug chemotherapy was administered. During radiotherapy for the primary lesion, progressive convulsions occurred suddenly. Computed tomography of the brain revealed metastasis in the frontal lobe. Brain metastasectomy was scheduled; however, endotracheal intubation was not possible because of the deformity of the glottis, and emergency tracheostomy was performed. Thereafter, granulation tissue proliferated in reaction to the tracheostomy cannulae in the trachea, and respiratory insufficiency persisted. Because of the rapid growth of an intrathoracic recurrent tumor, the patient passed away 2months after brain surgery. This is the first report of sarcoma in a patient with mucopolysaccharidosis. Respiratory management is difficult in patients with mucopolysaccharidosis, especially under general anesthesia. Orthopedic surgeons should be aware that surgical planning must be performed carefully when soft tissue sarcomas occur in patients with mucopolysaccharidosis.

Extraskeletal Ewing Sarcoma of the Gastrointestinal and Hepatobiliary Tract: Deceptive Immunophenotype Commonly Leads to Misdiagnosis.

Ewing sarcoma (ES) is an uncommon mesenchymal neoplasm that typically develops as a bone mass, although up to 30% arise in extraskeletal sites. ES of the gastrointestinal (GI) and hepatobiliary tract is rare and may be misdiagnosed as other, more common neoplasms that occur in these sites. However, the correct classification of extraskeletal ES is important for timely clinical management and prognostication. We reviewed our experience of ES in the GI and hepatobiliary tract in order to further highlight the clinicopathologic features of these neoplasms and document the potential for misdiagnosis in this setting. The archives and consultation files of 6 academic institutions were retrospectively queried for cases of ES occurring in the GI and hepatobiliary tract. The histologic slides and ancillary studies were reviewed and clinical data were retrieved for each case through the electronic medical records, when available. Twenty-three patients with ES in the GI and/or hepatobiliary tract were identified from 2000 to 2022. Of these, 11 were women and 12 were men with a median age of 38 years (range, 2 to 64). Tumor locations included the pancreas (n=5), liver (n=2), stomach (n=3), colorectum (n=3), and small intestine (n=5), as well as tumors involving multiple organs, pelvis and retroperitoneum (n=5). Tumor size varied between 2cm and 18cm. Twenty were primary and 3 were metastases. Of the 23 cases, only 17% were initially diagnosed as ES. The most common misdiagnoses involved various forms of neuroendocrine neoplasia due to expression of synaptophysin and other neuroendocrine markers (22%). A wide variety of diagnoses including GI stromal tumor was considered due to aberrant CD117 expression (4%). The diagnosis of ES was ultimately confirmed by detection of the EWSR1 rearrangement in 22 cases. The remaining case was diagnosed using traditional immunohistochemistry. Follow-up information was available in 20 cases, with follow-up time varying between 2 and 256 months. Six patients with follow-up died of disease between 6 and 60 months following initial presentation. Our data indicate ES in the GI and hepatobiliary tract is commonly misdiagnosed leading to a delay in therapy. In light of the attendant therapeutic and prognostic implications, ES should be considered in the differential diagnosis of any GI or hepatobiliary tumor with epithelioid and/or small round cell morphology.

Primary extraskeletal intradural Ewing sarcoma with acute hemorrhage: a case report and review of the literature

BackgroundSpinal cord tumors present a challenge in diagnosis and treatment due to their varied histopathological characteristics. While Ewing sarcoma is a rare malignant tumor typically originating from skeletal bone, cases of primary intradural extraskeletal Ewing sarcoma are exceptionally rare. The similarity of its presentation to other spinal tumors further complicates its identification and management.Case presentationWe report a case of a 58-year-old Palestinian male with intradural extraskeletal lumbar Ewing sarcoma. The patient initially presented with lower back pain and bilateral S1 radiculopathy, with more severe symptoms on the left side. Magnetic resonance imaging revealed a 7 cm oval-shaped mass with homogeneous contrast enhancement, obstructing the spinal canal from L3/L4 to L5/S1 levels. Initially, a myxopapillary ependymoma was suspected, but the patient’s sensory and motor functions suddenly deteriorated during hospitalization. Repeat magnetic resonance imaging indicated heterogeneous contrast enhancement, indicating acute intratumoral hemorrhage. Consequently, the patient underwent emergent L3–L5 laminotomy, with successful gross total resection of the tumor. Histopathological and immunohistochemical analyses confirmed the diagnosis of intradural extraskeletal Ewing sarcoma. Adjuvant therapy was administered to minimize the risk of local recurrence or distant metastasis. A systematic review of relevant literature, along with retrospective analysis of medical records, operative reports, radiological studies, and histopathological findings of similar cases, was also conducted.ConclusionsIntradural extraskeletal Ewing sarcoma is an infrequently encountered condition in adult patients, emphasizing the importance of considering it in the differential diagnosis of spinal tumors. Surgeons must possess a comprehensive understanding of this rare entity to ensure accurate staging and optimal management, particularly in the early stages when prompt intervention may improve prognosis.

Extraskeletal Ewing sarcoma arising from stomach and ovary: A case series of two rare sites

Ewing sarcoma is the second most common tumor in children and young adults. Primitive neuroectodermal tumors/Ewing sarcoma family consist of small round cell of neuroectodermal origin. Ewing sarcoma commonly arises from long bones and pelvic region but extraskeletal Ewing sarcoma (EES) is a very rare tumor with highly malignant potential associated with poor outcome. We present a case series of two cases, one is from the ovary in a 24-year-old young, married, multiparous woman who presented with metastatic disease and was treated with palliative chemotherapy. The second is an Ewing sarcoma arising from the stomach in a 33-year-old male who underwent surgery followed by adjuvant chemotherapy. EES is usually an uncommon tumor and many times, the diagnosis becomes delayed and presents with metastatic disease. Immunohistochemical and molecular analysis is a must to diagnose the EES. There are no standard treatment guidelines. Surgery, various chemotherapy regimens, and radiotherapy are given for treatment. Early diagnosis and interventions are required for better outcomes.

Rare origin - Ewing's sarcoma of the pleura: a case report and literature review

Ewing sarcoma (ES) was first reported by Ewing in 1921. It is the second largest malignant bone tumor in children and adolescents, typically occurring in the bones of trunk or limbs . Extraskeletal Ewing sarcoma (EES) was first reported by Tefft et al. in 1969 and is extremely rare, accounting for less than 1% of all sarcomas. It can occur in any part of soft tissue, mostly in the trunk and lower limbs, and rarely in the pleura. We report a 22-year-old case of extraosseous Ewing sarcoma of pleural origin discovered and pathologically confirmed by physical examination. We report its CT manifestations and pathological results, and review the literature to summarize and analyze the clinical and imaging characteristics of extraosseous Ewing sarcoma, in order to improve our understanding of the disease.

Extraskeletal Ewing sarcoma – A deceptive entity on imaging

ABSTRACT Background: Ewing sarcoma arising from soft tissue is referred to as an Extraskeletal ewing sarcoma (EES). It is a rare tumor that primarily affects young people and has an aggressive course with a high recurrence rate. Imaging findings of EES tumors are generally non-specific, with some variation based on location and the tissues involved. Case summary: We present two rare cases of EES in adolescent females: one from the right kidney masquerading as renal cell carcinoma (case 1), and the other one primarily arising from the left chest wall (case 2). Conclusion: EES, albeit rare, should be considered in patients with large, heterogeneous soft tissue masses. Radiologists should be aware of this deceptive entity because, despite its non-specific appearance, imaging can assist in determining tumor extent, surrounding infiltration, distant metastasis identification, surgical feasibility, and thus the best treatment options.

Primary Extraskeletal Ewing Sarcoma, Initially Misdiagnosed as a Neurogenic Tumor

Primary Extraskeletal Ewing Sarcoma, Initially Misdiagnosed as a Neurogenic Tumor

Clinical profile, outcomes and prognostic factors of extra-skeletal Ewing Sarcoma in children treated at a single institution in India

Clinical profile, outcomes and prognostic factors of extra-skeletal Ewing Sarcoma in children treated at a single institution in India

Ewing sarcoma: a tumor with an uncanny predilection for uncommon sites

Ewing sarcoma is one of the most common bone tumors diagnosed in pediatric age group second only to osteosarcoma. The tumor is known to involve most commonly pelvic bones and long bones while extra-skeletal Ewing sarcoma accounts for 15%. Ewing sarcoma of other sites like scapula, clavicle, hands, and feet are quite rare, accounting for only 3-5%. To determine the epidemiological profile of Ewing sarcoma of unusual sites treated in our department including age at diagnosis, site of origin and mode of management along with survival data. Details of Ewing sarcoma patients reported our department in last 9 years were collected and data was analysed. We report a total of 20 cases of Ewing sarcoma in last 9 years with 4 (20%) extra skeletal Ewing sarcoma arising from soft tissues of extremities and 30% from rare sites (3 scapula, 1 clavicle, 1 phalanx, 1 calcaneum). All patients were operated after 4-7 cycles of chemotherapy with 66% limb salvage rate. With an average necrosis of 40%, with a median follow up of 36 months, the overall survival of the group was found to be 77.7%. Ewing sarcoma is one of the rare tumors of bone and soft tissue with the predilection for unusual sites, with reasonable survival outcomes in localized disease. Though scapula, clavicle, hands and feet are rare sites for Ewing sarcoma, they accounted for 30% in our department, possibly because of the referral patterns.

Gastrointestinal Ewing Sarcoma: A Clinicopathological and Molecular Genetic Analysis of 25 Cases.

Occurrence of extraskeletal Ewing sarcoma (ES) in the gastrointestinal (GI) tract is extremely rare. Here, we report 25 cases of ES arising primarily in the GI tract with a focus on the clinicopathological and molecular features, differential diagnosis, and biological behavior. Thirteen patients (52%) were male, and 12 (48%) were female with age ranging from 9 to 59 years (mean: 36.2 years; median: 38 years). Twenty-one tumors (84%) occurred in the small intestine, 3 (12%) in the stomach, and 1 (4%) in the anal canal. At operation, 8/18 (44.4%) patients presented with abdominopelvic disseminated disease. Tumor size measured from 2 to 25cm (mean: 8.2cm; median: 6cm) in maximum size. Microscopically, the tumors were composed of infiltrative small round, ovoid, or short spindle cells arranged mostly in lobular and solid sheet-like patterns with a rich capillary vasculature. Focal formation of Homer Wright-type rosettes and pseudoalveolar architecture was noted each in 2 (8%) cases and 3 (12%) cases. Besides CD99 (25/25; 100%), Fli-1 (15/15, 100%), and NKX2.2 (14/16; 87.5%), the tumor cells also showed variable staining of CD117 (14/17; 82.4%). Of 25 cases, 23 (92%) demonstrated EWSR1 rearrangement by fluorescence in situ hybridization analysis. The 2 cases with negative fluorescence in situ hybridization results were found to harbor EWSR1::ERG and EWSR1::FLI1 fusion by further RNA sequencing, respectively, with a median follow-up of 12 months (range: 1 to 42 months), 5/19 (26.3%) patients developed visceral metastasis and 12/19 (63.2%) patients died of the disease (range:1 to 33 months; median: 9 months). This study showed that GI ES had a predilection for the small intestine, although other sites of the GI tract could also be involved. GI ES had a poor prognosis with a high rate of mortality, particularly in patients with abdominopelvic disseminated disease. In light of appropriate therapeutic strategies and prognostic considerations, it is essential not to misdiagnose GI ES as gastrointestinal stromal tumor owing to the expression of aberrant CD117.

S4003 Multiple Primary Bone Tumors in the GI Tract? Extra-Skeletal Ewing Sarcoma in the Stomach, Duodenum, and Pancreas

S4003 Multiple Primary Bone Tumors in the GI Tract? Extra-Skeletal Ewing Sarcoma in the Stomach, Duodenum, and Pancreas

Primary pancreatic Ewing sarcoma with metastases on FDG PET/CT

BackgroundEwing sarcoma (ES) is a highly aggressive malignant tumor most commonly affecting long bones. Extraskeletal Ewing sarcoma (EES) is a malignant tumor with aggressive behavior carrying bad prognosis with pancreas being an extremely rare primary site. We present a case of histopathologically proven EES of the pancreas in a young female who presented with abdominal pain. 18F-fluorodeoxyglucose positron emission tomography (18F FDG PET/CT) is a useful modality for detecting distant metastases in EES. It helps in diagnosis, localizing the primary, its extension, optimal treatment planning and evaluation of response to standard treatments available.Case presentationAn 18-year-old female presented with complaints of progressive abdominal pain and distention since 6 weeks. Physical examination was suggestive of a solid large mass in the upper left abdomen and decreased breath sounds with dullness in the left lower lung fields. On Contrast enhanced computed tomography (CECT) imaging, a large heterogeneously enhancing mass was seen arising from pancreas along with retroperitoneal lymphadenopathy. A moderate sized left sided pleural effusion with atelectasis of lower lobe of left lung was also noted. Histopathological analysis was suggestive of pancreatic ES following which the patient underwent five cycles of chemotherapy. Following this, she underwent 18F FDG PET/CT which showed hypermetabolic large mass arising from body and tail of pancreas with areas of internal necrosis along with left adrenal metastasis, retroperitoneal lymphadenopathy, a massive left pleural effusion and compressive atelectasis of left lower lobe. The patient expired within a week following PET/CT.ConclusionsEES most often presents in the late stage of the disease with vague symptoms. Timely diagnosis and initiation of treatment is of utmost importance considering the aggressiveness of the tumor. Establishing a diagnosis of Ewing sarcoma is especially difficult when the mass is arising from the pancreas. Imaging, histopathology and immunohistochemistry (IHC) play a key role in accurate diagnosis of such masses. 18F FDG PET/CT can be useful for detecting local and distant spread, operability, treatment planning and evaluation of response to chemotherapy.

Primary Extraskeletal Ewing Sarcoma of the Duodenum Revealed by 18 F-FDG PET/CT.

Extraskeletal Ewing sarcoma of the duodenum is a relatively uncommon entity tumor. We report a case of extraskeletal Ewing sarcoma in a 21-year-old woman. She complained of abdomen pain and melena. 18 F-FDG PET/CT showed an intense uptake by the duodenum mass along with multiple FDG-avid enlarged lymph nodes in the mesentery, which was pathologically proven as extraskeletal Ewing sarcoma.

CORR Insights®: Is Bone Marrow Aspiration and Biopsy of Clinical Importance in the Initial Staging of Extraskeletal Ewing Sarcoma?

1Professor and Chair, Department of Orthopedic Surgery, School of Medicine, National & Kapodistrian University of Athens, Attikon University General Hospital, Athens, Greece P. J. Papagelopoulos, National & Kapodistrian University of Athens, School of Medicine, Attikon University General Hospital, First Department of Orthopaedic Surgery, Neapoleos 15, Amarousion, Athens, 15123, Greece, Email: [email protected] This CORR Insights® is a commentary on the article “Is Bone Marrow Aspiration and Biopsy of Clinical Importance in the Initial Staging of Extraskeletal Ewing Sarcoma?” by Wahlig and colleagues available at: DOI: 10.1097/CORR.0000000000002661. The author certifies that there are no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article related to the author or any immediate family members. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writer, and do not reflect the opinion or policy of CORR® or The Association of Bone and Joint Surgeons®.

КОСТНАЯ И ВНЕСКЕЛЕТНАЯ САРКОМА ЮИНГА: СРАВНИТЕЛЬНАЯ ХАРАКТЕРИСТИКА ОСОБЕННОСТЕЙ ТЕЧЕНИЯ И ИСХОДОВ ЗАБОЛЕВАНИЯ (ОПЫТ НИИ ДЕТСКОЙ ОНКОЛОГИИ И ГЕМАТОЛОГИИ им. Л.А. ДУРНОВА)

Ewing's sarcoma (ES) is a highly malignant tumor of children and adolescents that affects bones and soft tissues with the same frequency. The origins of ES are the subject to many discussions. Differential diagnosis is complicated and requires a full range of immunohistochemical and molecular genetic studies. The prognostic value for extraskeletal and bone ES under current chemotherapy protocols is unknown and requires further analysis. The purposes of this research were a comparative analysis of clinical characteristics, therapeutic approaches and outcomes of the disease in patients with extraskeletal and bone localizations of ES. Materials and methods used: a single-center retrospective cohort study was conducted, which included 330 patients (237 (71.8%) boys/93 (28.2%) girls) aged 0 to 18 y/o (median 11 [7; 14] y/o) with confirmed diagnosis of ES who received treatment in 2008-2022, of which 280 (84.85%) with primary bone localization (group of bone ES - BES), and 50 (15.15%) with soft tissue localization (group of extraskeletal ES - ESES). Comparative analysis of survival rates for primary tumor localization in the area of bones and soft tissues was performed. The median follow-up time for all patients was 35.5 [18.2; 68.5] months, 37.0 [18.0; 71.0] months with BES, and 29.5 [16.8; 65.5] months with ESES. All patients received treatment according to the protocols adopted at the Research Institute of Pediatric Oncology and Hematology named after Academician L.A. Durnov with the N.N. Blokhin Russian Cancer Research Center (Moscow, Russia): MMES-99, ES-2017. Overall survival (OS) was calculated with the Kaplan-Meier estimator. Results: the selected groups differed statistically significantly by gender (74% of boys in the BES group, and 60% of boys the ESES group, p=0.035) and age (10.5 [8; 15] years in the BES group, and 8.5 [4; 12] y/o in the ESES group, p=0.001). BES was diagnosed statistically significantly more often in older age groups than ESES (p=0.004). Compared with BES, in ESES the tumor was statistically significantly more often located in the region of the axial skeleton and visceral organs (24.0% vs. 56%, p<0.001). Disseminated form of the disease in the BES group was recorded in 110 (39.3%) patients, and in 15 (30.0%) in the ESES group. Authors did not find statistically significant differences in overall 5-year OS for localized forms of BES and ESES (79% and 78.5%, respectively), the median OS in these groups was not reached. The OS of patients with disseminated stages of BES and ESES was statistically significantly lower than in the group of localized forms. At the same time, the 5-year OS was 41.2% and 40.6%, the median OS was 46.9 and 28.4 months (p=0.001, respectively). Differences in 5-year progression-free survival (PFS) for localized forms were 71.6% for BES and 75.6% for ESES (p=0.001), for disseminated forms - 32.4% vs. 44.9% (p=0.036, respectively). In the disseminated stage of BES, progression/relapse was detected in 50% of cases after 21.1 months, and after 20.3 months for ESES. Conclusions: Authors have identified the following unfavorable prognostic factors. As for BES these were: older age, disease stage, primary tumor volume over 200 cm3 and length over 8 cm, radiation therapy in the treatment program or combined treatment. As for ESES, the unfavorable PFS factors were the stage of the disease, the volume of the primary tumor and the process dissemination. In this regard additional analysis of key genomic characteristics is required in order to further determine the risk group stratification and prognosis.