Combinatorial macrophage induced innate immunotherapy against Ewing sarcoma: Turning "Two Keys" simultaneously.

BACKGROUND: Macrophages play important roles in phagocytosing tumor cells. However, tumors escape macrophage phagocytosis in part through the expression of anti-phagocytic signals, most commonly CD47. In Ewing sarcoma (ES), we found that tumor cells utilize dual mechanisms to evade macrophage clearance by simultaneously over-expressing CD47 and down-regulating cell surface calreticulin (csCRT), the pro-phagocytic signal. Here, we investigate the combination of a CD47 blockade (magrolimab, MAG) to inhibit the anti-phagocytic signal and a chemotherapy regimen (doxorubicin, DOX) to enhance the pro-phagocytic signal to induce macrophage phagocytosis of ES cells in vitro and inhibit tumor growth and metastasis in vivo. METHODS: Macrophages were derived from human peripheral blood monocytes by granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF). Flow cytometry- and microscopy-based in-vitro phagocytosis assays were performed to evaluate macrophage phagocytosis of ES cells. Annexin-V assay was performed to evaluate apoptosis. CD47 was knocked out by CRISPR/Cas9 approach. ES cell-based and patient-derived-xenograft (PDX)-based mouse models were utilized to assess the effects of MAG and/or DOX on ES tumor development and animal survival. RNA-Seq combined with CIBERSORTx analysis was utilized to identify changes in tumor cell transcriptome and tumor infiltrating immune cell profiling in MAG and/or DOX treated xenograft tumors. RESULTS: We found that MAG significantly increased macrophage phagocytosis of ES cells in vitro (p < 0.01) and had significant effect on reducing tumor burden (p < 0.01) and increasing survival in NSG mouse model (p < 0.001). The csCRT level on ES cells was significantly enhanced by DOX in a dose- and time-dependent manner (p < 0.01). Importantly, DOX combined with MAG significantly enhanced macrophage phagocytosis of ES cells in vitro (p < 0.01) and significantly decreased tumor burden (p < 0.01) and lung metastasis (p < 0.0001) and extended animal survival in vivo in two different mouse models of ES (p < 0.0001). Furthermore, we identified CD38, CD209, CD163 and CD206 as potential markers for ES-phagocytic macrophages. Moreover, we found increased M2 macrophage infiltration and decreased expression of Cd209 in the tumor microenvironment of MAG and DOX combinatorial therapy treated tumors. CONCLUSIONS: By turning "two keys" simultaneously to reactivate macrophage phagocytic activity, our data demonstrated an effective and highly translatable alternative therapeutic approach utilizing innate (tumor associated macrophages) immunotherapy against high-risk metastatic ES.

SETD8 inhibits apoptosis and ferroptosis of Ewing's sarcoma through YBX1/RAC3 axis.

Ewing's sarcoma (ES) represents a rare yet exceedingly aggressive neoplasm that poses a significant health risk to the pediatric and adolescent population. The clinical outcomes for individuals with relapsed or refractory ES are notably adverse, primarily attributed to the constrained therapeutic alternatives available. Despite significant advancements in the field, molecular pathology-driven therapeutic strategies have yet to achieve a definitive reduction in the mortality rates associated with ES. Consequently, there exists an imperative need to discover innovative therapeutic targets to effectively combat ES. To reveal the mechanism of the SETD8 (also known as lysine methyltransferase 5A) inhibitor UNC0379, cell death manners were analyzed with different inhibitors. The contributions of SETD8 to the processes of apoptosis and ferroptosis in ES cells were evaluated employing the histone methyltransferase inhibitor UNC0379 in conjunction with RNA interference techniques. The molecular regulatory mechanisms of SETD8 in ES were examined through the application of RNA sequencing (RNA-seq) and mass spectrometry-based proteomic analysis. Moreover, nude mouse xenograft models were established to explore the role of SETD8 in ES in vivo. SETD8, a sole nucleosome-specific methyltransferase that catalyzes mono-methylation of histone H4 at lysine 20 (H4K20me1), was found to be upregulated in ES, and its overexpression was associated with dismal outcomes of patients. SETD8 knockdown dramatically induced the apoptosis and ferroptosis of ES cells in vitro and suppressed tumorigenesis in vivo. Mechanistic investigations revealed that SETD8 facilitated the nuclear translocation of YBX1 through post-transcriptional regulatory mechanisms, which subsequently culminated in the transcriptional upregulation of RAC3. In summary, SETD8 inhibits the apoptosis and ferroptosis of ES cells through the YBX1/RAC3 axis, which provides new insights into the mechanism of tumorigenesis of ES. SETD8 may be a potential target for clinical intervention in ES patients.

Pediatric Axial Ewing Sarcoma: A Retrospective Population-Based Survival Analysis.

INTRODUCTION: Ewing sarcomas of the axial skeleton represent a notable challenge for clinicians because of their aggressive presentation and tendency to obstruct neurovascular structures; however, little data exist regarding axial tumors in children. This study is the first population-based analysis assessing treatment regimens for axial Ewing sarcomas and their effects on cancer-specific survival and overall survival (OS). METHODS: Data from 2004 to 2019 were collected for all patients aged 1 to 24 years from the Surveillance, Epidemiology, and End Results (SEER) database. Primary groups included pelvic tumors, thoracic tumors, and vertebral tumors. Chi-squared and Kaplan-Meier tests were used to assess associations between demographic variables, clinical and treatment characteristics, and patient survival. RESULTS: Pelvic tumors were most common, and 49.7% received chemotherapy/radiation. Vertebral tumors were least common, and 56.7% received chemotherapy/surgery/radiation. 53.5% of thoracic tumors received chemotherapy/surgery. Surgery was most common for thoracic tumors (80.2%) and rare for pelvic tumors (38.9%). Radiation therapy was most common for vertebral tumors (83.6%) and least common for thoracic tumors (36.0%). Pelvic tumors exhibited the lowest OS (1-year, 5-year, and 10-year OS: 96%, 70%, and 59%), followed by thoracic tumors (1-year, 5-year, and 10-year OS: 97%, 79%, and 66%) and vertebral tumors (1-year, 5-year, and 10-year OS: 92%, 77%, and 68%). CONCLUSION: This study underpins the importance of both early detection and chemotherapy-based multimodal therapy in the treatment of axial Ewing sarcoma in a pediatric population. A comparatively large decline in OS was observed between 5 and 10 years for patients with thoracic tumors, and this cohort's 10-year OS has not improved when compared with a similar SEER cohort from 1973 to 2011. Despite a growing body of research supporting definitive radiation therapy, a notable portion of patients with pelvic Ewing sarcoma did not receive radiation, representing an unmet need for this population.

Human EWS-FLI protein levels and neomorphic functions show a complex, function-specific dose-response relationship in Drosophila.

Ewing sarcoma (EwS) is a cancer that arises in the bones and soft tissues, typically driven by the Ewing's sarcoma breakpoint region 1-Friend leukemia virus integration 1 (EWS-FLI) oncogene. Implementation of genetically modified animal models of EwS has proved difficult largely owing to EWS-FLI's high toxicity. The EWS-FLI1FS frameshift variant that circumvents toxicity but is still able to perform key oncogenic functions provided the first study model in Drosophila. However, the quest for Drosophila lines expressing full-length, unmodified EWS-FLI remained open. Here, we show that EWS-FLI1FS's lower toxicity is owed to reduced protein levels caused by its frameshifted C-terminal peptide, and report new strategies through which we have generated Drosophila lines that express full-length, unmodified EWS-FLI. Using these lines, we have found that the upregulation of transcription from GGAA-microsatellites (GGAAµSats) presents a positive linear correlation within a wide range of EWS-FLI protein concentrations. In contrast, rather counterintuitively, GGAAµSats-independent transcriptomic dysregulation presents relatively minor differences across the same range, suggesting that GGAAµSat-dependent and -independent transcriptional upregulation present different kinetics of response with regards to changing EWS-FLI protein concentration. Our results underpin the functional relevance of varying EWS-FLI expression levels and provide experimental tools to investigate, in Drosophila, the effect of the EWS-FLI 'high' and 'low' states that have been reported and are suspected to be important for EwS in humans.

Efficacy of an expandable prosthesis placement after left pneumonectomy for soft tissue Ewing sarcoma in a 5-year-old child: 10 years follow-up.

We report the case of a 5-year-old girl who underwent left pneumonectomy for Ewing sarcoma of the lung. Two expandable prostheses were placed in the left hemi-thorax to prevent post-pneumonectomy syndrome and to protect the heart from radiotherapy. With a follow-up of 10 years, the procedure proved to be effective both on post-pneumonectomy syndrome and on cardiac protection.

Extraosseous Ewing Sarcoma Manifesting as an Acute Abdomen in a Young Adult Male: a Case Report.

Ewing sarcoma is a tumor primarily affecting children and young adults, and usually affects long bones. Extraosseous Ewing sarcoma (EES) is a rare primary tumor of soft tissues. We present a case of abdominal EES with metastasis to thoracic cavity, which presented as abdominal pain and vomiting in a 21-year-old previously healthy gentleman.

Germline variants in patients diagnosed with pediatric soft tissue sarcoma.

BACKGROUND: While soft tissue sarcomas affect younger patients, few studies have assessed the distribution of underlying pathogenic germline variants. PATIENTS AND METHODS: We retrospectively identified all pediatric and young adult patients (0-22 years) at Haukeland University Hospital, Norway (1981-2019), through clinical and pathological records. We identified n = 46 eligible patients. From these 46 patients, adequate material representing normal tissue was available for n = 41 cases (n = 24 diagnosed with rhabdomyosarcoma, 9 with synovial sarcomas, 2 with Ewing sarcomas, and 6 without further classification), with matching tumor tissue for n = 40. Normal tissue samples were analyzed for germline pathogenic variants (PVs) by targeted sequencing of 360 cancer genes. RESULTS: Out of the 41 analyzed cases, we found PVs or likely PVs in 7 (17%). These variants were found in TP53, MUTYH, FANCC, DICER1, FANCA, MYO3A, and MYO5B. Supporting the causality of these PVs, four cases revealed loss of heterozygosity (LOH) of the wild-type allele in the tumor tissue, one patient with a PV in DICER1 had a second somatic variant in DICER1, and a patient with a PV in TP53 had the altered allele amplified in the tumor. For three out of five with available family history, a history of other cancers in relatives was recorded. Among genes with variants of uncertain significance, CHD1L was of particular interest, revealing a stop-gain and a missense variant. INTERPRETATION: A high fraction of young patients with soft tissue sarcoma harbor PVs. Among the genes affected, we substantiate a potential role of MYO5B and propose a potential role for MYO3A.

Cadherin-11 contributes to the heterogenous and dynamic Wnt-Wnt-ß-catenin pathway activation in Ewing sarcoma.

Ewing sarcoma is the second most common bone cancer in children, and while patients who present with metastatic disease at the time of diagnosis have a dismal prognosis. Ewing sarcoma tumors are driven by the fusion gene EWS/Fli1, and while these tumors are genetically homogenous, the transcriptional heterogeneity can lead to a variety of cellular processes including metastasis. In this study, we demonstrate that in Ewing sarcoma cells, the canonical Wnt/ß-Catenin signaling pathway is heterogeneously activated in vitro and in vivo, correlating with hypoxia and EWS/Fli1 activity. Ewing sarcoma cells predominantly express ß-Catenin on the cell membrane bound to CDH11, which can respond to exogenous Wnt ligands leading to the immediate activation of Wnt/ß-Catenin signaling within a tumor. Knockdown of CDH11 leads to delayed and decreased response to exogenous Wnt ligand stimulation, and ultimately decreased metastatic propensity. Our findings strongly indicate that CDH11 is a key component of regulating Wnt//ß-Catenin signaling heterogeneity within Ewing sarcoma tumors, and is a promising molecular target to alter Wnt//ß-Catenin signaling in Ewing sarcoma patients.

Diagnosis and management of cancer therapy-related myocarditis in a young female: A case report and review of literature.

BACKGROUND: The treatment of choice for Extra-osseous Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET), a rare neoplasm, is the VAC/IE regimen. This regimen includes Doxorubicin, Vincristine, Cyclophosphamide, Ifosfamide, and Etoposide, all of which have cardiotoxic effects. Myocarditis, a potentially threatening side effect following cancer therapy, can be accurately managed and diagnosed. CASE PRESENTATION: In the current study, we report the case of a 19-year-old female with a mass on the abdominal wall, diagnosed with ES/PNET. She was treated with the VAC/IE regimen. A month after the last session of chemotherapy, she experienced dyspnea. Upon evaluation, a high level of troponin and a low left ventricular ejection fraction (LVEF) were detected via transthoracic echocardiography. She was treated with anti-heart failure drugs, but the response was unsatisfactory. The possibility of Cancer therapy-related myocarditis was suspected, and cardiac magnetic resonance imaging (CMR) confirmed acute myocarditis. This patient exhibited a significant response to intravenous immunoglobulin (IVIG), with her LVEF improving from 30-35% to 50% within three months. CONCLUSION: In this case, based on negative tests and the absence of viral signs and symptoms, Cancer therapy-related myocarditis is highly suspected as the cause of myocarditis. This case underscores the importance of accurately utilizing CMR as a non-invasive method for diagnosing myocarditis. It effectively highlights the identification of reversible myocarditis with appropriate treatment and the notable response to IVIG, suggesting its potential as a favorable treatment for myocarditis in younger patients.

Extraskeletal ewing's sarcoma on hard palate biltaerally: A rare case report.

Ewing Sarcoma belongs to the category of undifferentiated blue small round cell tumour and its origin has been traced to be that from inside of the bone, but can also arise in soft tissues (extraosseous form). These lesions belong to the category of round cell tumours, which includes a varied range of tumours. This category, although found in other extremities and thoracic regions, head and neck region have been reported to have less number of tumours, in addition to that the soft tissue counterparts are even scarcely reported. Thereby, this case reports represents a soft tissue counterpart of Ewings Sarcoma on the hard palate, which not only extends unilaterally but extends bilaterally.

Co-targeting JAK1/STAT6/GAS6/TAM signaling improves chemotherapy efficacy in Ewing sarcoma.

Ewing sarcoma is a pediatric bone and soft tissue tumor treated with chemotherapy, radiation, and surgery. Despite intensive multimodality therapy, ~50% patients eventually relapse and die of the disease due to chemoresistance. Here, using phospho-profiling, we find Ewing sarcoma cells treated with chemotherapeutic agents activate TAM (TYRO3, AXL, MERTK) kinases to augment Akt and ERK signaling facilitating chemoresistance. Mechanistically, chemotherapy-induced JAK1-SQ phosphorylation releases JAK1 pseudokinase domain inhibition allowing for JAK1 activation. This alternative JAK1 activation mechanism leads to STAT6 nuclear translocation triggering transcription and secretion of the TAM kinase ligand GAS6 with autocrine/paracrine consequences. Importantly, pharmacological inhibition of either JAK1 by filgotinib or TAM kinases by UNC2025 sensitizes Ewing sarcoma to chemotherapy in vitro and in vivo. Excitingly, the TAM kinase inhibitor MRX-2843 currently in human clinical trials to treat AML and advanced solid tumors, enhances chemotherapy efficacy to further suppress Ewing sarcoma tumor growth in vivo. Our findings reveal an Ewing sarcoma chemoresistance mechanism with an immediate translational value.

Novel Dual Bicolumnar Fibula Graft Reconstruction of Distal Humerus in Pediatric Patients After Massive Bone Resection: A Report of Two Cases.

CASE: We describe 2 case studies, involving a 10-year-old girl with an aneurysmal bone cyst and a 12-year-old adolescent boy with Ewing sarcoma. The patient with Ewing sarcoma was previously managed with wide surgical excision and fibular graft reconstruction and subsequently experienced significant graft resorption, hardware failure, and fracture 24 months after operation. A revision limb salvage attempt was undertaken. In both cases, fibular strut grafts were harvested and fixed with intramedullary k-wires to recreate the medial and lateral columns of the distal humeral triangle. CONCLUSION: The technique achieved complete osseous integration, structural support, and functional restoration of the elbow in both cases, with good functional outcomes.

[Ewing sarcoma/primitive hepatic neuroectodermal tumor]. / Sarcoma de Ewing/tumor neuroectodérmico primitivo hepático.

Ewing sarcoma (ES) and primitive neuroectodermal tumor (PNET) belong to the group of neoplasms called small round cell tumors. PNETs have been divided into central and peripheral. ES and peripheral PNETs arise from bones, soft tissues, or peripheral nerves. We present a case of hepatic ES/PNET in a healthy man that began four months before consultation with abdominal symptoms and weight loss. Upper gastrointestinal endoscopy and laboratory tests revealed no notable findings. The abdominal tomography revealed an enlarged liver due to a solid lesion that involved all its segments with intravenous contrast enhancement and large areas of necrosis. It compressed and displaced neighboring structures. Core needle biopsy of the liver lesion was performed: small round cell neoplasm. Immunohistochemistry revealed negativity for CD45, CKA1/A3, chromogranin, synaptophysin, and cytokeratins CK7 and CK20. Dim CD56 expression and CD99, FLI-1, and NKX2 positivity. He underwent chemotherapy treatment with carboplatin and etoposide for 6 cycles with clinical improvement and tolerance. Control images showed reduction of the mass with involvement of the right hepatic lobe, involvement of the inferior vena cava, infiltration of the right adrenal gland and upper pole of the right kidney. He was referred to hepatobiliary surgery for surgical resection of the residual lesion. The patient rejected the proposed surgical procedure. Our objective is to highlight the clinical and histological diagnostic challenge of this entity that requires ruling out other clinical entities.

El sarcoma de Ewing (ES) y el tumor neuroectodérmico primitivo (PNET) pertenecen al grupo de neoplasias denominadas tumores de células pequeñas y redondas. Los PNET se dividen en centrales y periféricos. El ES y los PNET periféricos surgen del tejido óseo, de los tejidos blandos o nervios periféricos. Presentamos un caso de ES/PNET hepático en un hombre sano que inició cuatro meses antes de la consulta con síntomas abdominales y pérdida de peso. La endoscopia digestiva alta y la analítica no revelaron hallazgos relevantes. En la tomografía de abdomen se evidenció hígado aumentado de tamaño a expensas de lesión sólida que comprometía todos sus segmentos con realce al contraste endovenoso y grandes áreas de necrosis. Comprimía y desplazaba estructuras vecinas. Se realizó biopsia con aguja gruesa de la lesión hepática: neoplasia de células pequeñas y redondas. La inmunohistoquímica reveló negatividad para CD45, CKA1/A3, cromogranina, sinaptofisina y citoqueratinas CK7 y CK20. Expresión tenue de CD56 y positividad de CD99, FLI-1 y NKX2. Realizó tratamiento quimioterápico con carboplatino y etopósido por 6 ciclos con mejoría clínica y tolerancia al mismo. En imágenes de control se evidenció reducción de la masa con afección del lóbulo hepático derecho, compromiso de la vena cava inferior, infiltración de la glándula suprarrenal y polo superior del riñón derechos. Se remitió a cirugía hepatobiliar para resección quirúrgica de la lesión residual. El paciente rechazó el procedimiento quirúrgico. Nuestro objetivo es destacar el desafío diagnóstico clínico e histológico de esta entidad que obliga a descartar otras entidades clínicas.

Differential cyclin-E1 expression in CIC-rearranged sarcoma.

CIC-rearranged sarcoma (CRS) is a group of high-grade undifferentiated small round cell sarcomas examined as a separate entity in the current WHO classification; since it shows more aggressive clinical behavior and distinct morphological and molecular features compared to Ewing sarcoma (ES). As CCNE1 expression is associated with tumor growth in CIC::DUX4 sarcomas, we aimed to demonstrate the value of cyclin E1 expression in CRS. Cyclin E1 immunohistochemistry and break-apart FISH for EWSR1 and CIC gene rearrangements were performed on 3-mm tissue microarrays composed of 40 small round cell tumors. Five cases were classified as CRS, whereas 22 were ES and 13 were unclassified (EWSR1-/CIC-). Among all three diagnostic groups, we found cyclin E1 expression level to be higher in CRS (80 %) and unclassified groups (61.5 %) compared to ES (4.5 %, p < 0.001). In addition, high cyclin E1 expression levels were associated with higher mean age at diagnosis, presence of atypical histology and myxoid stroma, low CD99 expression, and presence of metastasis at diagnosis. The sensitivity and specificity of high cyclin E1 expression in detecting non-ES cases were 95.5 % and 66.7 %, respectively. However, the correlation between cyclin E1 expression level and survival was not statistically significant. This is the first study that shows cyclin E1 immunohistochemical expression in EWSR1-negative undifferentiated small cell sarcomas, particularly CRS.

Primary Ewing's sarcoma of the uterine cervix: a case report and review of the literature.

BACKGROUND: Ewing's sarcoma (ES) is an aggressive cancer of bone and soft tissue, most of which tend to occur in the bone. Extraosseous Ewing's sarcoma (EES) of the cervix is extremely rare. CASE PRESENTATION: In the present work, we reported a 39-year-old cervical EES patient with a 2.5*2.1*1.8 cm tumor mass. According to previous literatures, our case is the smallest tumor found in primary cervical ES ever. The patient initially came to our hospital due to vaginal bleeding, and then the gynecological examination found a neoplasm between the cervical canal and partially in the external cervical orifice. The diagnosis of EES was confirmed below: Hematoxylin & Eosin staining (H&E) revealed small round blue malignant cells in biopsy specimens. Immunohistochemistry (IHC) showed the positive staining for CD99, NKX2.2, and FLI1. Disruption of EWSR1 gene was found by fluorescence in situ hybridization (FISH), and the EWSR1-FLI1 gene fusion was determined by next-generation sequencing (NGS). The patient received laparoscopic wide hysterectomy, bilateral adnexectomy, pelvic lymphadenectomy, and postoperative adjuvant chemotherapy and remained disease free with regular follow-up for 1 year. CONCLUSIONS: Through a systematic review of previously reported cervical ES and this case, we highlighted the importance of FISH and NGS for the accuracy of ESS diagnosis, which could assist on the optimal treatment strategy. However, due to the rarity of the disease, there is no standard treatment schemes. Investigation on molecular pathological diagnosis and standardization of treatment regimens for cervical ES are critical to patients' prognosis.

Emerging therapies in Ewing sarcoma.

PURPOSE OF REVIEW: There is an unmet need to improve outcomes for patients for Ewing sarcoma, a rare, aggressive sarcoma with a peak incidence in adolescents and young adults (AYA). Current therapy at diagnosis involves multiagent chemotherapy and local therapy, but despite intensification of treatment, those with metastases at diagnosis and recurrent disease have poor outcomes. RECENT FINDINGS: Improved understanding of Ewing sarcoma biology has identified novel targets with promising activity in Ewing sarcoma patients, including tyrosine kinase inhibitors that are now undergoing evaluation as combination and maintenance therapy. Other emerging therapies include those that target the EWSR1::FLI1 fusion oncoprotein, and act on DNA damage, cell cycle and apoptotic pathways. Immunotherapeutic approaches, particularly CAR-T-cell therapy directed at GD2, also hold promise. Recent collaborative clinical trials that have defined an international standard of care for patients with newly diagnosed Ewing sarcoma and novel platform studies with adaptive designs offer unique opportunities to investigate these therapies inclusive of all ages. SUMMARY: Close international collaboration between clinicians and biologists will allow us to prioritize promising emerging therapies and develop biomarkers to facilitate their incorporation into standard of care and more rapidly translate into benefit for Ewing sarcoma patients.

A Systemic Review of Primary Malignant Long Bone Tumors in Children and Adolescents.

PURPOSE OF THE STUDY: Managing bone tumours is complex, relying on limited evidence, expert opinions, and retrospective reviews. Multidisciplinary approaches and early diagnosis are crucial for better outcomes, especially in young patients with growing skeletons. The aim of this systemic review and meta-analysis is to give a comprehensive review of common malignant tumors affecting long bones in children and adolescents. MATERIAL AND METHODS: A PubMed/Medline search for "primary malignant long bone tumours in children" initially retrieved 1120 papers, which were subsequently narrowed down to 110 articles based on inclusion and exclusion criteria. These articles were reviewed, focusing on clinical presentation, diagnostic workup, treatment options, surgical planning, and variations in presentation, including rare tumours. The two most commonly reported tumours were osteosarcoma and Ewing sarcoma, leading to the division of studies into five groups. The inclusion criteria encompassed malignancies in patients aged 2-25 years, work-up, imaging, surgical treatment, rare tumour case reports, and surgical management principles, resulting in a heterogeneous group of articles. To enhance categorisation, it was clarified that studies with 10 or more cases were considered retrospective reviews. RESULTS: Reviewing of results thus demonstrate that the two likely tumours in children under consideration were osteosarcoma and Ewing sarcoma. Their presentation findings and clinical features were discussed in detail in the review. It is worth noting here that in case of differential diagnosis this should be the first on the list. DISCUSSION AND CONCLUSIONS: Although focus of literature is more on the two most common tumours. However, rare tumours should be considered as they can mimic these common tumors. KEY WORDS: primary, malignant, bone tumors, children, adolescent.

Can FDG-PET assess the response to chemotherapy and predict tissue necrosis in osteosarcoma and Ewing sarcoma?

INTRODUCTION: Osteosarcoma (OS) and Ewing sarcoma (ES) represent the pediatric population's most common malignant bone tumors. 18-Fluorodeoxyglucose positron emission tomography has been shown to be effective in both the diagnostic and staging phases of cancer treatment. In recent years, some studies have also explored the possibility that FDG-PET could have a prognostic role.

Ewing Sarcoma of the Female Genital Tract: Clinicopathologic Analysis of 21 Cases With an Emphasis on the Differential Diagnosis of Gynecologic Round Cell, Spindle, and Epithelioid Neoplasms.

Ewing sarcoma is an uncommon neoplasm considered in the differential diagnosis of tumors with "small round cell" morphology, but its occurrence in the gynecologic tract has only been sporadically documented. Herein, we describe the largest cohort of Ewing sarcoma localized to the female genital tract to date, and emphasize their clinicopathologic resemblance to more common gynecologic neoplasms. Ewing sarcoma (n=21) was retrospectively identified from 5 institutions. The average patient age was 35 (range 6-61) years. Tumor sites included uterus (n=8), cervix (n=4), vulva (n=5), vagina (n=1), broad ligament (n=1), inguinal area (n=1), and pelvis (n=1). Nine of 18 cases in which slides were available for review demonstrated only classic round cell morphology, with the remainder showing a variable combination and prominence of variant ovoid/spindle or epithelioid appearance. Tumors showed diffuse membranous reactivity for CD99 (20/20) and were positive for NKX2.2 (8/8, diffuse) and cyclin D1 (7/7, of which 3/7 were patchy/multifocal and 4/7 were diffuse). They were negative for ER (0/6) and CD10 (0/6). Three cases were initially diagnosed as endometrial stromal sarcomas. EWSR1 rearrangement was confirmed in 20/21 by fluorescence in situ hybridization (n=15) and/or sequencing (n=8). Of the eight tumors that underwent sequencing, 6 harbored FLI1 , 1 ERG, and 1 FEV as the fusion partner. Of 11 patients with available follow-up, 5 died of disease, 1 developed lung metastases and 5 are alive with no evidence of disease. Ewing sarcoma of the gynecologic tract is a rare, aggressive entity that shares some morphologic and immunohistochemical features with other more common gynecologic neoplasms. In addition to the typical round cell appearance, variant spindled/ovoid to epithelioid morphology may also be observed and should prompt consideration of this entity with appropriate immunohistochemical and/or molecular studies.