Soft Tissue Tumors In Children Research Articles

Pleomorphic Rhabdomyosarcoma of the Uterine Corpus in an Adult Who Underwent Multi-gene Panel Testing.

Rhabdomyosarcoma (RMS) is the most common malignant soft tissue tumor in children. Adult primary RMS of gynecological origin is a rare condition and uterine RMS is an aggressive malignancy with a poor prognosis. The genetic variants associated with uterine RMS in adults have yet to be fully elucidated, and there is no established therapeutic strategy for rare tumors. A 69-year-old Japanese woman was referred to our hospital with abdominal bloating. Imaging examination revealed a tumor with diameter of 85 mm located in the uterus and multiple regional lymph node metastases. Biopsy of the uterine corpus indicated possible uterine carcinosarcoma or RMS. Following debulking surgery, the patient was diagnosed with stage IVB pleomorphic RMS. The patient was treated with two courses of doxorubicin every three weeks and one course of combination chemotherapy with vincristine, actinomycin, and cyclophosphamide. Because of rapid progression of the disease, we decided to perform multi-gene panel testing to determine the most effective therapeutic strategy. However, no therapeutic plan based on genetic information was identified. The patient with chemotherapy-refractory RMS died 11 weeks after surgery. Our patient had advanced uterine RMS with an unresectable tumor that was resistant to chemotherapy, resulting in poor outcomes. Despite conducting multi-gene panel testing, no tailored therapeutic approach based on genetic information was found. This case highlights the challenges in managing uterine RMS in adults and underscores the urgent need for further research to identify effective treatment modalities.

Embryonal rhabdomyosarcoma of hard palate: a case report and review of literature

Rhabdomyosarcomas are the most common malignant soft tissue tumors in children and adolescents. Around 40% of cases are diagnosed in head and neck region with orbit and face being the commonly involved areas. Oral lesions account for less than 10%. We report a case of embryonal RMS in a 4-year-old boy who presented with a polypoid mass in the hard palate. Though majority of the oral lesions encountered in children are benign, a small but significant percentage may be representative of an aggressive malignant tumor. Differentiating benign and malignant oral lesions is mandatory for optimal diagnostic strategies.

18F‐FDG PET/CT findings of paratesticular alveolar rhabdomyosarcoma

AbstractRhabdomyosarcoma (RMS) originates from primitive mesenchymal cells and is the most common soft tissue tumor in childhood. 18F‐fluoro‐deoxyglucose (18F‐FDG) positron emission tomography (PET)/computed tomography (CT) has been reported to be valuable in RMS staging and risk stratification. Paratesticular RMS is a relatively uncommon form of RMS, most of which are of the embryonal histologic type. Paratesticular alveolar RMS is associated with aggressive behavior, high metastatic potential, and poor outcomes. To the best of our knowledge, 18F‐FDG PET/CT imaging findings of paratesticular alveolar RMS have never been described. Here, we report on a 16‐year‐old boy's rare paratesticular alveolar RMS with multiple metastases and its findings on 18F‐FDG PET/CT. This case also demonstrates the potential value of 18F‐FDG PET/CT in RMS staging and treatment decisions, and may aid in the differential diagnosis.

Fat-Containing Soft Tissue Tumors in Children, Adolescents, and Young Adults: Which Require Biopsy?

To confirm the overall benignity of fat-containing soft tissue tumors (STT) on a pediatric cohort and to define the clinical and imaging features that warrant a biopsy. A retrospective monocentric study was conducted on patients aged less than 25 years consecutively referred for fat-containing STT to our Comprehensive Cancer Center between 1998 and 2022. Tumor imaging characteristics at diagnosis (US, CT, or MRI) were correlated with pathology. The database extraction identified 63 fat-containing tumors with clinical, histologic, and imaging data available for review. In total, 58 (92%) were benign tumors: 36 lipoblastomas and lipomas, 12 fibrous hamartomas of infancy (FHI), 5 lipofibromatosis, 2 lipomas arborescens, 2 lipomatosis and 1 spindle-cell lipoma. Five patients (8%) were diagnosed with liposarcoma. Factors significantly correlated with malignancy were age >10 years old (p < 0.001), having a cancer-predisposing condition (p < 0.001), a percentage of fat <25% (p = 0.002), and a presence of myxoid zones (p < 0.001) on imaging. Most fat-containing STT in children may be classified as benign tumors based on clinics and imaging. The indication for biopsy could be limited to patients aged 10 years or more with either a cancer-predisposing condition or imaging features demonstrating either a low-fat component (<25%) or the presence of myxoid zones.

Abstract 6736: Suppression of antigen presentation is a hallmark of pediatric rhabdomyosarcoma

Abstract Background: Rhabdomyosarcoma (RMS) is the most common soft tissue tumor in children and young adults, accounting for approximately 350-400 new cases annually in the US. These tumors are diagnosed based on their expression of skeletal muscle lineage markers. Clinical trials testing conventional immunotherapies such as cancer vaccines or immune checkpoint blockade (ICB) therapy have found no activity in RMS, although the root causes of failure are largely unexplored. A recent study by our group found that RMS tumors have a lack of immune infiltrate, consistent with previous reports. However, we made an unexpected observation that RMS tumors had a near absence of antigen processing and presentation (APP) gene expression, a key requisite for anti-tumor CD8+ T lymphocytes. In this study, we investigate the root causes of the lack of APP in RMS and evaluate implications for immunotherapy. Methods: Publicly available DNA sequencing datasets were used to evaluate APP gene mutations in RMS tumor samples. RNAseq from reporter iPSC cell lines demarcating specific stages of skeletal muscle differentiation were used to evaluate APP gene expression during myogenesis. Surface MHC class I expression was evaluated using flow cytometry against a panel of pediatric sarcoma cell lines. RMS PDX and cell line APP protein levels were measured by western blot. Stimulation of APP in RMS cell lines was tested using IFNγ or sub-cytotoxic doses of different epigenetic therapeutics (DNMTi, HDACi, EZH2i) before analyzing surface MHC class I expression by flow cytometry. Results: RNAseq analysis of the differentiation states across the normal human skeletal muscle lineage revealed a myoblastic cell state which transiently downregulates the APP pathway. RNA expression of HLA-A,B,C genes were lower in RMS than any other pediatric extracranial solid tumor histology studied. RMS cell lines and PDX models also displayed low APP pathway gene expression by western blot and flow cytometry, with FOXO1 fusion positive RMS having a near absence of expression. RMS tumor exome sequencing data from RMS patients showed a lack of enrichment of APP gene mutations. Instead, we found that APP could be induced in nearly all samples tested using IFNγ or epigenetic stimulation with Decitabine, Entinostat, or Tazemetostat. Conclusions: We uncovered a previously unappreciated lack of antigen presentation in RMS which phenocopies myoblasts in normal skeletal muscle development. The downregulation of MHC class I antigen presentation is not due to APP pathway mutations but rather a partially reversible downregulation mirroring this specific stage of normal skeletal muscle development. Our findings suggest that pharmacological reversal of the APP pathway downregulation may enhance immunotherapies targeting MHC class I antigens in RMS. Citation Format: David Milewski, Meijie Tian, Yong Kim, Jun Wei, Javed Khan. Suppression of antigen presentation is a hallmark of pediatric rhabdomyosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6736.

Birth-related soft tissue injury due to transverse malpresentation at delivery: a case report

Abstract Objectives Birth-related mechanical trauma to the newborn is an important issue and may be underestimated [Chaturvedi A, Chaturvedi A, Stanescu AL, Blickman JG, Meyers SP. Mechanical birth-related trauma to the neonate: an imaging perspective. Insights Imag 2018;9:103–18]. Risk factors for birth-related injuries include vacuum or forceps delivery, large size for gestational age and abnormal presentation before delivery [Gupta R, Cabacungan ET. Neonatal birth trauma: analysis of yearly trends, risk factors, and outcomes. J Pediatr 2021;238:174–80]. When a newborn has a soft tissue mass, there is a wide range of potential diagnoses, ranging from benign traumatic origins to aggressive phenotypes of malignant tumors [Thacker M. Benign soft tissue tumors in children. Orthop Clin N Am 2014;44:433–44]. Diagnosing a congenital tumor in a newborn creates uncertainty for parents and health care providers. Accurate imaging is crucial for distinguishing soft tissue mass origins. Case presentation A 32 weeks 6 days pregnant Caucasian woman was admitted after premature prelabor rupture of membranes (PPROM). Fetal ultrasound showed no abnormalities, the infant was born by a caesarean section. The delivery was complicated by the infant’s transverse position. A female infant was born with a large left-sided dorsal soft tissue mass at the thoracic level with elastic consistency, and multiple skin lacerations. A broad differential diagnosis was made. Additional imaging was suggestive for a posttraumatic swelling due to transverse position during birth. The mass decreased and disappeared over three days. Conclusions The diagnosis of a soft tissue mass in a newborn can be challenging. A birth-related trauma affecting the soft tissue should be considered, especially if prenatal ultrasound findings were normal. Malpresentation during birth is a significant risk factor. Accurate diagnostic imaging is important to do before conducting further diagnostic examinations. The time course of the mass, before and after birth, can aid in determining its origin.

Primary rhabdomyosarcoma of the breast in an adult: A role of volumetric modulated arc technique radiotherapy

Rhabdomyosarcoma (RMS) is the most common soft tissue tumor in children and is rarely seen in adults. It is slightly more common in females. It constitutes <1% of all breast malignancies. Radiologically, it is difficult to differentiate RMS from other breast benign or malignant tumors. Hence, it is often diagnosed late. Immunohistochemistry staining with actin, desmin, myogenin, and myoD1 confirms the diagnosis. There is no standard treatment due to rarity of cases. Role of radiotherapy is still controversial, but many studies have shown the benefit of radiotherapy in large tumors of more than 5 cm. RMSs are usually aggressive tumors with survival ranging from 3 months to 7 years. Here, we report a case of primary RMS of the breast in a 49-year-old female, describing radiological and pathological features and treatment with volumetric modulated arc technique radiotherapy.

Early propranolol treatment of infantile hemangiomas improves outcome

BackgroundInfantile hemangiomas (IH) are the most common soft tissue tumors of childhood. Although most of these tumors are not worrisome, some IH may be life or function-threatening, can lead to permanent disfigurement, or have associated structural congenital anomalies, requiring early recognition and referral to specialists for treatment consideration. Since 2008, oral propranolol has been widely considered to be the first-line treatment for IH. ObjectivesTo evaluate aesthetic and functional outcome in propranolol-treated infantile hemangiomas according to the age of treatment onset. MethodsRetrospective, observational study of infantile hemangioma patients under 4 years of age at the time of diagnosis, treated with oral propranolol. Evaluated parameters included: pre and post-treatment morphologic/aesthetic aspects of the hemangioma, total resolution rate, degree of functional compromise of affected areas and its evolution. Two independent pediatric dermatologists evaluated all cases reviewing clinical data from medical records and comparing clinical photographs taken at initiation and at the end of treatment of each patient. Data were analyzed with STATA 13.0 program. ResultsThe cohort included 138 patients, with a female predominance. The median age at therapy onset was 3 months. The morphological/aesthetic improvement rate was 99% (95% CI 96‒99), the total resolution rate was 48% (95% CI 44‒60) and the functional improvement rate reached 100%. When comparing total resolution outcome versus age when treatment started, the improvement was larger in younger patients (3.5 vs. 4.9 months, p = 0.01). When comparing the total resolution rate in those younger or older than 3 months at treatment initiation, the percentage of total resolution in the younger group was 57% vs. 40% in the older one (p = 0.05). Study limitationsRetrospective design; patients photographs were the sole indicators used to measure regression rates. Visual assessment is subjective. ConclusionThe present results strongly suggest that early (before 3 months of age) initiation of treatment of infantile hemangiomas with propranolol results in significantly higher aesthetic and functional improvement rates and a higher percentage of total resolution.

MSS05 Presentation Time: 4:05 PM: HDR Brachytherapy for Pediatric Vaginal Rhabdomyosarcoma: Two Case Reports with Long-Term Follow Up

<h3>Purpose</h3> Rhabdomyosarcomas (RMS) are the most common soft tissue tumor in children with over 400 cases diagnosed each year. Vaginal RMS is exceedingly rare, accounting for 4% of all RMS and 10% of female RMS. Outcomes are favorable with 10-year overall survival rates estimated to be over 90%. Current standard of care requires multidisciplinary approach involving chemotherapy and local therapy. To limit late effects from treatment, local therapy has advanced from radical surgeries to no local treatment in those with complete response or favoring radiation therapy for those with residual disease following chemotherapy. There is limited data on modern brachytherapy techniques for the management of vaginal RMS. Here we report two cases of pediatric vaginal RMS treated with HDR intracavitary brachytherapy at our institution and long-term follow up. <h3>Methods and Materials</h3> Following IRB approval, we identified two pediatric patients who were treated at our institution with HDR brachytherapy for RMS between 2017 and 2019 and had follow up data available. We collected demographics, presenting information, treatment data including chemotherapy, surgery if applicable, brachytherapy plans, and outcomes. <h3>Results</h3> Both patients presented at outside hospitals at the age of 2 with a prolapsing vaginal mass. Biopsies were consistent with botryoid vaginal RMS. They were referred to our institution for consideration of radiation therapy after completion of 12 weeks of VAC-based chemotherapy. Post-chemotherapy MRIs were obtained to assess extent of residual disease and a vaginal applicator was placed at the time of MRI for HDR brachytherapy planning. Both patients had good response with small areas of residual thickening along the vaginal wall. The first patient underwent exam under anesthesia, vaginal dilation and removal of visualized gross disease prior to brachytherapy. A 2.2 cm Syed obturator was used with a straight central tandem positioned at the proximal end of the obturator for central loading with 2 additional flexible catheters placed in the posterior grooves of the Syed obturator. The 3 channels allowed for coverage of the posterior and proximal vaginal disease seen on her post-chemotherapy MRI. On her last fraction, she was noted to have vaginal swelling and difficulty with inserting the Syed obturator, therefore, a 2 cm Varian single channel cylinder was used for her last fraction. For the second patient, a custom designed vaginal cylinder was made by machining a hole through a 1.3 cm vaginal dilator with a catheter inserted and affixed in the central canal. Both patients were prescribed 4.9 Gy x 6 fractions treated three times weekly with the goal of obtaining an equivalent total dose of 36 Gy with 45 Gy to the vaginal surface. The first patient was prescribed to 5mm depth and the second patient to 3mm depth based on extent of residual disease. Both patients tolerated treatment well with minimal bleeding on cylinder insertion and expected acute side effects including cystitis, dysuria and acute vaginal discomfort that resolved with sitz baths and barrier ointments. With 4 and 3 years follow up, respectively, both patients have no evidence of disease on MRI imaging and no evidence of long-term toxicities related to their brachytherapy. <h3>Conclusions</h3> Vaginal RMS is a rare cancer and thus there is limited modern experience with HDR brachytherapy as a means for local control in this patient population. Here were present two cases where devices relatively common in gynecologic brachytherapy practices can be used and customized to cover small tumors in pediatric patients. Our experience has shown that for select patients, HDR brachytherapy can be a safe, tolerable, and efficacious treatment modality for vaginal RMS.

Regulation of Metastasis in Ewing Sarcoma.

Simple SummaryEwing sarcoma (EwS) is the second most common bone and soft tissue cancer which mainly happens in children and adolescents. Currently, EwS patients are treated with a combination of surgery, radiation, and interval compressed chemotherapy. While outcomes have improved over the last several decades for patients with localized diseases, little progress has been made in the treatment of patients with newly diagnosed metastatic or relapsed diseases. Moreover, in localized cases, the survival rates are around 70% after five years and 30% after ten years. However, one third of patients develop metastatic tumor and, when metastasis is diagnosed, the five-year survival rates drop sharply to 25%. There is, therefore, urgent need to dissect the regulatory mechanism of EwS tumor metastasis and thus develop treatment strategies to treat metastatic diseases. Here, we reviewed the regulation of metastasis in EwS and hoped this can guide future studies on metastasis.Ewing sarcoma (EwS) is a type of bone and soft tissue tumor in children and adolescents. Over 85% of cases are caused by the expression of fusion protein EWSR1-FLI1 generated by chromosome translocation. Acting as a potent chimeric oncoprotein, EWSR1-FLI1 binds to chromatin, changes the epigenetic states, and thus alters the expression of a large set of genes. Several studies have revealed that the expression level of EWSR1-FLI1 is variable and dynamic within and across different EwS cell lines and primary tumors, leading to tumoral heterogeneity. Cells with high EWSR1-FLI1 expression (EWSR1-FLI1-high) proliferate in an exponential manner, whereas cells with low EWSR1-FLI1 expression (EWSR1-FLI1-low) tend to have a strong propensity to migrate, invade, and metastasize. Metastasis is the leading cause of cancer-related deaths. The continuous evolution of EwS research has revealed some of the molecular underpinnings of this dissemination process. In this review, we discuss the molecular signatures that contribute to metastasis.

Abstract A036: Surfaceome profiling of rhabdomyosarcoma reveals B7-H3 as a mediator of immune evasion

Abstract Introduction: Pediatric rhabdomyosarcoma (RMS) is the most common soft tissue tumor in children, with nearly 20% of children presenting with locally aggressive and/or metastatic disease. Despite aggressive chemotherapy and radiotherapy, the 5-year overall survival rate is still less than 40%. In addition, resistance to chemotherapy remains the major cause of cancer-related mortality. Therefore, there is an unmet need to develop more effective and tolerable therapeutic strategies for the treatment of RMS. Our overall objective is to leverage transcriptomic and proteomic profiling methods to identify RMS-specific surface proteins targetable with immune-based therapies. Methods: To identify therapeutic targets, we performed cell-surface capture and mass spectrometry on fusion-positive (FP), fusion-negative (FN) RMS and normal skeletal muscle. Transcriptomic datasets of RMS tumor specimens and normal tissue were employed to identify high-confidence RMS-specific cell-surface proteins. Expression of immune checkpoint molecules was confirmed by flow cytometry, western blot and PCR. Paraffin-embedded tissue sections were used to determine protein expression and prognostic value in RMS patients. We developed an in vitro T-cell killing assay to assess the functional role of immune checkpoint molecules on the antitumor immune response. Results: Surfaceome profiling of RMS cells revealed unique protein signatures specific for each tumor type and normal tissue. We have identified 5061 cell-surface proteins in RMS and 31.6% of proteins were correctly located at the plasma membrane. By integrating proteomic and transcriptomic data, we have identified 30 and 38 proteins significantly overexpressed in fusion-negative and fusion-positive RMS respectively compared to normal muscle. We have identified the immune checkpoint molecule B7-H3 as cell-surface protein overexpressed in both RMS subtypes. Strong expression of B7-H3 was also observed in patient’s tumor specimens. Genetic deletion of B7-H3 gene in RMS cells was associated with higher antitumor immune response in tumor cells co-cultured with CD8+-T cells. No difference was observed in tumor cell proliferation and radioresistance. Conclusions: Through integrated transcriptomic and proteomic profiling, we have discovered B7-H3 as a key regulator of tumor immune-evasion in RMS. B7-H3 is a suitable immunotherapy target for the treatment of RMS. Further studies are warranted to elucidate underlying mechanisms of B7-H3 function in RMS. Citation Format: Roxane R. Lavoie, Fabrice Lucien, Patricio C. Gargollo, Mohamed E. Ahmed, Yohan Kim, Emily Baer, Doris Phelps, Cristine M. Charlesworth, Benjamin J. Madden, Liguo Wang, Peter J. Hougthon, John Cheville, Haidong Dong, Candace F. Granberg. Surfaceome profiling of rhabdomyosarcoma reveals B7-H3 as a mediator of immune evasion [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr A036.

Abstract 5756: Next-generation sequencing (NGS) reveals different molecular profiles of pediatric sarcoma in children and adults

Abstract Background: Pediatric sarcomas represent approximately 12% of all pediatric cancers with over 100 subtypes. Although some molecular detection techniques can be used to assist the diagnosis and treatment of pediatric sarcoma, it still remains challenging due to overlapping morphological features and limited biopsy specimens. Here we performed next generation sequencing (NGS) to analyze the molecular profiles of pediatric and adult sarcomas in China. Methods: A total of 700 Chinese patients with sarcoma were collected. The tumor tissue and matching blood specimens were tested by the integrative DNA and RNA sequencing panel Onco Panscan plus࣪ at Genetronhealth. Results: Of the 700 sarcoma patients, there were 224 children (32%) and 476 adults (68%). Difference from the almost same ratio of men to women in adults, there were more males (n = 134) than females (n = 90) in children. Rhabdomyosarcoma was the most common soft tissue tumor in children, accounting for 24.1% (n = 54), followed by Ewing's sarcoma (9.8%, n = 22) and Osteosarcoma (8.5%, n = 34), while Angiosarcoma (3.8%, n = 18) and Fibrosarcoma (3.6%, n = 17) were the most common in adults. Based on mutation types, the frequent alterations were missense mutations (n = 326, 51.2%), fusions (n = 129, 20.3%) and copy number variants (n = 66, 10.4%) in children with a mean of 3 mutations per patient, and missense mutations (n = 1438, 66.8%), fusions (n = 221, 10.3%) and truncating mutations (n = 215, 10.0%) in adults with an average 5 mutations. TP53 (12.9%, n = 29), EWSR1 (8.9%, n = 20) and ALK mutations (6.7%, n = 15) were common in children, which was distinct from TP53 (29.4%, n = 140), NF1 (4.8%, n = 23), CTNNB1 (4.2%, n = 20) and RB1 (4.2%, n = 20) in adults. Based on NGS results, pathological subtypes could be confirmed in 40.2% (90/224) and 48.1% (229/476) of children and of adults sarcoma patients, respectively. In addition, we identified a total of 72 drug-targeted gene mutations in the 57 children patients, of which 35 (48.6%) gene mutations could be targeted by FDA-approved drugs. In adults, 256 drug-targeted gene mutations were detected and the proportion of actionable mutations was up to 78.9% (n = 202). Conclusion: The genomic landscape of pediatric sarcomas is different from that of adults. NGS aids in the subtype classification and clinical guidance of pediatric sarcomas, providing evidence for personalized treatments with clinical benefit. Citation Format: Weisong Cai, Fang Liu, Xuejiao Liu, Xiaojuan Wang, Chunyang Wang, Tonghui Ma, Shu Li. Next-generation sequencing (NGS) reveals different molecular profiles of pediatric sarcoma in children and adults [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5756.

Abstract 466: Predicting survival of rhabdomyosarcoma patients based on deep learning of H&amp;E images

Abstract Background: Rhabdomyosarcoma (RMS) is an aggressive soft tissue tumor in children and young adults, accounting for 350-400 new cases annually in the US. Diagnosis of RMS is defined by the expression of genes related to skeletal muscle differentiation and can be further subclassified based on histological patterns (embryonal, ERMS; alveolar, ARMS; spindle/sclerosing, SSRMS). Genetic studies have found that the presence of a PAX fusion gene (FP-RMS), which is present in many ARMS tumors, correlates with poor outcome. Subsequent studies have identified additional genetic alterations (ex. TP53 or MYOD1 mutations) which also display distinct histological features and are associated with poor outcome. As a result, there is a growing need to identify these mutations to improve risk stratification. The goal of this study is to develop and test deep learning algorithms from diagnostic H&amp;E images of RMS tumors which can aid in the diagnosis, mutation prediction and risk stratification for RMS patients. Methods: De-identified RMS patient samples were collected from tissue banking studies from Children’s Oncology Group (n=275), University Hospital Zurich (n=250) and Memorial Sloan Kettering (n=10). H&amp;E stains on whole slides or TMAs were digitally scanned and used for analysis. Clinical information including clinical risk group, event-free survival, and genomic findings were used as available for training and testing. Convolutional neural networks (CNN) using EfficientNet were trained using K-fold cross validation to classify tumor histology, mutation probability, and risk stratification and tested against randomly selected samples or independent datasets when available. Results: The developed AI algorithm was able to classify tissue as ARMS (FP-RMS), ERMS (FN-RMS), stroma and necrosis with an average weighted intersect-over-union of 0.74 when compared to an expert pathologist annotation. A second deep learning algorithm developed specifically for distinguishing FP-RMS from FN-RMS displayed excellent sensitivity (FP-RMS=0.88) and specificity (FP-RMS=0.86) when tested against an independent RMS TMA dataset. Algorithms were also trained to predict mutations in MYOD1, RAS pathway genes, and TP53 and displayed good performance with ROC values of 0.96, 0.68, and 0.64, respectively. Lastly, we developed an algorithm to provide a Cox proportional hazard prediction based on H&amp;E images. The resulting algorithm was capable of predicting EFS with similar accuracy as current clinical risk group assessment with improved ability to distinguish intermediate and high risk patients. Conclusions: Deep learning with convolutional neural networks provides pathologist-independent classification of RMS patients from simple H&amp;E images. These AI algorithms can provide probabilities of prognostically relevant genetic alterations and survival which will ultimately contribute to better risk stratification of RMS patients. Citation Format: David Milewski, Hyun Jung, G. Thomas Brown, Yanling Liu, Jack Collins, Marc Ladanyi, Erin Rudzinski, Javed Khan. Predicting survival of rhabdomyosarcoma patients based on deep learning of H&amp;E images [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 466.

Point-of-Care Ultrasound Assessment of Orbital Rhabdomyosarcoma in a Pediatric Patient.

Rhabdomyosarcoma is the most common soft tissue tumor in children and orbital lesions account for 10% of these diagnoses. This case describes a young boy who presented with eyelid swelling that was initially concerning for an expanding hematoma given a history of recent trauma to the eye. Point-of-care ultrasound identified 2 distinct lesions surrounding the globe, which prompted further investigation, including ophthalmology consult and computed tomography. The case presented highlights the initial misdiagnosis on both point-of-care ultrasound and computed tomography and the importance of using color Doppler on ultrasound to distinguish an orbital rhabdomyosarcoma from a posttraumatic hematoma.

Lipofibromatosis: Central Nervous System Involvement by a Benign Neoplasm

Background: Lipofibromatosis is a relatively new entity, considered in the differential diagnosis of soft tissue tumors in children, involving mainly the extremities. Most cases can be completely resected without recurrence. Atypical forms have been described and their highly infiltrative capability can lead to severe clinical impairment. Case report: We report an infant with rapidly growing posterior cervicothoracic tumor, extending from the bulbo-medullary junction to T6 vertebra, leading to loss of spontaneous breathing, quadriparesis and devastating long-term consequences. Spinal tomography scan at 35 days suggested myelomeningocele. Prenatal and early postnatal ultrasounds were reviewed and no central nervous system involvement or fusion defects were present. Magnetic resonance at 40 days showed infiltrative mass, later confirmed by pathology as lipofibromatosis. Two resections failed to completely remove the tumor. Discussion: Lipofibromatosis can involve critical structures in the central nervous system and is difficult to treat surgically in those circumstances.

Deep Learning of Rhabdomyosarcoma Pathology Images for Classification and Survival Outcome Prediction

Rhabdomyosarcoma (RMS), the most common malignant soft tissue tumor in children, has several histologic subtypes that influence treatment and predict patient outcomes. Assistance with histologic classification for pathologists as well as discovery of optimized predictive biomarkers is needed. A convolutional neural network for RMS histology subtype classification was developed using digitized pathology images from 80 patients collected at time of diagnosis. A subsequent embryonal rhabdomyosarcoma (eRMS) prognostic model was also developed in a cohort of 60 eRMS patients. The RMS classification model reached a performance of an area under the receiver operating curve of 0.94 for alveolar rhabdomyosarcoma and an area under the receiver operating curve of 0.92 for eRMS at slide level in the test data set (n=192). The eRMS prognosis model separated the patients into predicted high- and low-risk groups with significantly different event-free survival outcome (likelihood ratio test; P =0.02) in the test data set (n=136). The predicted risk group is significantly associated with patient event-free survival outcome after adjusting for patient age and sex (predicted high- versus low-risk group hazard ratio,4.64; 95% CI,1.05-20.57; P =0.04). This is the first comprehensive study to develop computational algorithms for subtype classification and prognosis prediction for RMS histopathology images. Such models can aid pathology evaluation and provide additional parameters for risk stratification.

Single Nuclear RNA Sequencing Highlights Intra-Tumoral Heterogeneity and Tumor Microenvironment Complexity in Testicular Embryonic Rhabdomyosarcoma.

BackgroundTesticular embryonic rhabdomyosarcoma (ERMS) is a rare soft tissue tumor in children featured with high intra-tumoral heterogeneity. In this study, we aimed to comprehensively delineate the testicular ERMS intra-tumoral heterogeneity and tumor microenvironment.MethodsCell types and the corresponding marker genes were identified by single-nuclear RNA sequencing (snRNA-seq). Functional states of different clusters were evaluated by uniform manifold approximation and projection and differentially expressed genes. Kaplan–Meier curve analysis was constructed according to the gene expression profile to determine the correlation between candidate marker genes and the overall survival and disease-free survival of patients with osteosarcoma from TCGA.ResultsA total of 8868 tumor cells and 10,147 normal cells were obtained from testicular ERMS tissues. The heterogeneous malignant subtype was composed of six subgroups (C1–C6) with differential proliferative and migratory potentials. Cell trajectory analysis revealed the C1 subgroup might be the starting cells of the tumor and transform into two different types of malignant cells, C2 and C5/6, during the development of RMS. The differentially expressed genes were closely related to cell adhesion and extracellular matrix signaling pathways. Furthermore, the interaction analysis between cell subgroups (macrophages and tumor cells, endothelial cells and tumor cells) demonstrated that collagen-related gene COL6A1 plays a key role from the initiation of ERMS to the entire process of malignant transformation.ConclusionOur findings provide a new insight in the understanding of the initiation and progression of testicular ERMS and have potential value in the development of markers for the diagnosis and stratification of testicular ERMS.

Paratesticular Rhabdomyosarcoma in a 30 Months Old Child at the Lagoon Mother and Child Teaching Hospital (CHUMEL) in Cotonou

Introduction: Rhabdomyosarcoma is the most common soft tissue tumor in children. Modern multidisciplinary approaches make it possible to better characterize the different entities and to adapt the treatment accordingly. Paratesticular localization is rare and aggressive. We report here a case of paratesticular localization in a 30 months old boy. Observation: The parents would have noticed a small, painless and rapidly evolving testicular mass in the 6 months old child. Not having health insurance, they went to the hospital only 5 months later. This was followed by a total ablation of the mass (without orchidectomy) and a pleiomorphic rhabdomyosarcoma had been concluded. No chemotherapy was performed and the mass recurred 2 months later. This time, its ablation was followed by a series of non-adapted chemotherapy sessions with irregular follow-ups leading 8 months later to the child’s admission at our department. He presented with a degraded general condition, associating an infectious and anemic syndrome, an important increase of the scrotal mass and the occurrence of a tumoral mass in the left iliac fossa. The tumoral nature of these masses was confirmed on abdominal ultrasound and scan. The tumor was classified stage II (TNM: initial Tumors, Nodes, Metastasis). The multidisciplinary medical staff indicated a total ablation of the two masses, followed by a new session of adapted chemotherapy, in the absence of radiotherapy means. The child died in the immediate surgery follow-ups due to cardiac arrest. Conclusion: In our context of insufficient technical facilities, only early detection and adapted imperative chemotherapy, would have enabled a durable remission in front of the paratesticular rhabdomyosarcoma.

The Effect of Direct and Indirect EZH2 Inhibition in Rhabdomyosarcoma Cell Lines.

Simple SummaryRhabdomyosarcoma is the most common soft tissue tumor in children. Its two major subtypes show epigenetic alterations that are associated with poor prognosis. Therefore, targeting these epigenetic alterations by pharmacological intervention could be a therapeutic approach. We investigated two different types of substances that interfere with the epigenetic process of histone methylation. We performed studies in two cell lines that carry characteristics of the major rhabdomyosarcoma subtypes. The aim of this study was to find out if the substances differ in their effect on tumor-related cellular functions and to find out if the tumor subtypes differ in their response to the substances. These findings may contribute to a better assessment of the feasibility of pharmacological intervention directed against histone methylation in subtypes of rhabdomyosarcoma.Enhancer of Zeste homolog 2 (EZH2) is involved in epigenetic regulation of gene transcription by catalyzing trimethylation of histone 3 at lysine 27. In rhabdomyosarcoma (RMS), increased EZH2 protein levels are associated with poor prognosis and increased metastatic potential, suggesting EZH2 as a therapeutic target. The inhibition of EZH2 can be achieved by direct inhibition which targets only the enzyme activity or by indirect inhibition which also affects activities of other methyltransferases and reduces EZH2 protein abundance. We assessed the direct inhibition of EZH2 by EPZ005687 and the indirect inhibition by 3-deazaneplanocin (DZNep) and adenosine dialdehyde (AdOx) in the embryonal RD and the alveolar RH30 RMS cell line. EPZ005687 was more effective in reducing the cell viability and colony formation, in promoting apoptosis induction, and in arresting cells in the G1 phase of the cell cycle than the indirect inhibitors. DZNep was more effective in decreasing spheroid viability and size in both cell lines than EPZ005687 and AdOx. Both types of inhibitors reduced cell migration of RH30 cells but not of RD cells. The results show that direct and indirect inhibition of EZH2 affect cellular functions differently. The alveolar cell line RH30 is more sensitive to epigenetic intervention than the embryonal cell line RD.

Small-molecule inhibitor - tyrphostin AG1296 regulates proliferation, survival and migration of rhabdomyosarcoma cells.

Rhabdomyosarcoma (RMS) is the most commonly occurring malignant soft tissue tumor in children. Despite improving its treatment methods, the current outcome in the advanced stages of this tumor is not satisfactory. RMS cells are characterized by abnormal cellular signaling due to the changes in the activity of the tyrosine kinases. Thus, substances blocking the mitogenic signal transmitted by receptors with tyrosine kinase activity raise hopes for inhibition of the uncontrolled cell growth. In this study, we examined the anticancer activity of tyrphostin AG1296, a tyrosine kinase inhibitor that binds to the intracellular domain of the PDGF (platelet-derived growth factor) receptor in human RMS alveolar and embryonal cell lines. We have discovered that tyrphostin AG1296 completely inhibited cell proliferation and effectively inhibited cell viability. Tyrphostin AG1296 induced apoptosis of the RMS cells and significantly inhibited their migration. Additionally, investigated inhibitor slightly inhibited expression of AKT and phosphorylation of ERK in alveolar RMS cells. Importantly, the inhibitor exerted also potent effects on the nanomechanical properties and cytoskeleton organization of RMS cells. To conclude, tyrphostin AG1296 is a promising compound in the treatment of alveolar RMS. Undoubtedly, a better knowledge of receptor pathomechanism of tyrosine kinases may contribute to developing new, more effective ways of RMS treatment.