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A 12 years-old, male indigenous dog was presented to Shahedul Alam Qaderi Teaching Veterinary Hospital (SAQTVH) in Chattogram, Bangladesh with a large tumour on its right front leg. The histopathological findings of the tumour were highly suggestive of an alveolar rhabdomyosarcoma (ARMS). The tumour was surgically removed from the dog. While there had been no recurrence for 5 months, the patient died 5 months post-operatively. The cause of the death and presence of metastasis could not be confirmed as follow-up investigations were declined by the owner. A histopathological study showed poorly differentiated neoplastic mononuclear cells forming nests in an alveolar pattern. Despite that the limited resources prevented myogenin staining for diagnostic confirmation, the well-contained, defined appearance of the tumour supports the diagnosis of ARMS. This report highlights the challenges in diagnosing and treating ARMS in indigenous dogs and emphasizes the need for further research and diagnostic markers to improve detection and management., (© 2024 The Author(s). Veterinary Medicine and Science published by John Wiley & Sons Ltd.)

RMS is a malignant tumor of soft tissues affecting primarily children and adolescents. Around 6% to 23% RMS patients present bone marrow infiltration but leukemia-like involvement is very rare; in these patients cytomorphology on bone marrow smears can lead to misdiagnosis. Differential diagnosis with alveolar RMS should be kept in mind in every pediatric patient presenting with a marked bone marrow involvement in the absence of typical lymphoproliferative findings., Competing Interests: The authors declare no conflict of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Secondary metastasis of rhabdomyosarcoma (RMS) to the orbit from a distant primary site is extremely rare in adults. In this article, we describe the case of a 24-year-old male presenting with proptosis, diplopia, and headaches concurrently with a histologically confirmed diagnosis of PAX3-FOXO1 positive paraspinal alveolar rhabdomyosarcoma. An orbital MRI revealed a fusiform mass arising from the inferior rectrus, displaying necrotic and irregular morphology consistent with malignancy. The patient is currently undergoing intensive chemotherapy. The objective of this case report is to highlight the rarity of an extraocular metastasis of RMS in an adult patient, alongside the importance of considering metastatic disease in a patient with fulminant unilateral proptosis.

Receptor tyrosine kinases (RTKs) serve as molecular targets for the development of novel personalized therapies in many malignancies. In the present study, expression pattern of receptor tyrosine kinases and its clinical significance in orbital RMS has been explored. Eighteen patients with histopathologically confirmed orbital RMS formed part of this study. Comprehensive q-PCR gene expression profiles of 19 RTKs were generated in the cases and controls. The patients were followed up for 59.53 ± 20.93 years. Clustering and statistical analysis tools were applied to identify the significant combination of RTKs associated with orbital rhabdomyosarcoma patients. mRNA overexpression of RTKs which included MET, AXL, EGFR was seen in 60-80% of cases; EGFR3, IGFR2, FGFR1, RET, PDGFR1, VEGFR2, PDGFR2 in 30-60% of cases; and EGFR4, FGFR3,VEGFR3 and ROS,IGFR1, EGFR1, FGFR2, VEGFR1 in 10-30% of cases. Immunoexpression of MET was seen in 89% of cases. A significant association was seen between MET mRNA and its protein expression. In all the cases MET gene expression was associated with worst overall survival (P = 0.03).There was a significant correlation of MET mRNA expression with RET, ROS, AXL, FGFR1, FGFR3, PDGFR1, IGFR1, VEGFR2, and EGFR3 genes. Association between MET gene and collective expression of RTKs was further evaluated by semi-supervised gene cluster analysis and Principal component analysis, which showed well-separated tumor clusters. MET gene overexpression could be a useful biomarker for identifying high risk orbital rhabdomyosarcoma patients. Well-separated tumor clusters confirmed the association between MET gene and collective expression of RTK genes. Therefore, the therapeutic potential of multi-kinase inhibitors targeting MET and the 9 other significant RTKs needs to be explored., (© 2023. The Author(s) under exclusive licence to Japan Human Cell Society.)

Objective: In this study, we investigate the molecular rearrangement of FOXO1 in alveolar rhabdomyosarcoma (ARHS) in Saudi pediatric patients. Method: We performed a molecular detection of molecular translocation in 30 pediatric cases of ARHS using FOXO1 dual color break-apart FISH probe (ZytoLight®, 13q14.11) and PAX5 dual color break-apart FISH probe (ZytoLight®, 9p13.2). Results: All analyzable cases of ARHS demonstrated FOXO1 translocation whereas PAX5 translocation was not detected in any case. Conclusion: Although the testing for PAX5 rearrangement was based on protein-protein network analysis, our study showed that PAX5 translocation is not conspicuous in ARHS. PAX7/3::FOXO1 fusion genes feature ARMS, rendering crossreactivity between PAX7 and PAX3 a possible explanation. Nevertheless, PAX5 immunoreactivity and molecular translocation could be an adjunctive pathway that is confined to aggressive ARMS.

Background: Anomalies of the FOXO1 gene in alveolar rhabdomyosarcoma are associated with a worse clinical prognosis, which determines the high value of studying the status of this gene when choosing a therapy strategy. The «gold standard» for determining FOXO1 gene rearrangements is currently the fluorescent in situ hybridization (FISH) technique., Objective: Study of the relationship between canonical FOXO1 translocation and immunohistochemical expression of new surrogate markers in alveolar rhabdomyosarcoma to determine their predictive value., Material and Methods: 139 cases of rhabdomyosarcoma were retrospectively studied. The study used tissue matrix technology (TMA). On sections obtained from TMA blocks, the FISH technique was implemented using the locus-specific probe MetaSystems XL FOXO1 Break Apart (Metasystems, Germany). Immunohistochemical studies were performed on similar sections from TMA blocks with OLIG2 (Cell Marque Antibodies, clone 211F1.1) and MUC4 (Cell Marque Antibodies, clone 8G7) antibodies., Results: The final expression analysis and statistical processing using a 2x2 contingency table and Fisher's exact test passed 111 cases (76 without FOXO1 rearrangement and 35 with rearrangement). The specificity of OLIG2 and MUC4 expression for FOXO1-rearranged alveolar rhabdomyosarcoma was 85.53% and 80.26%, respectively ( p <0.01)., Conclusion: The present study confirms the high predictive value of the expression of surrogate markers OLIG2 and MUC4 in determining the genetic status of alveolar rhabdomyosarcoma, which makes it possible to predict with high specificity the detection of the FOXO1 gene rearrangement.

Rhabdomyosarcoma of the larynx has been very rarely described in pediatric population. There are 3 histological subtypes: embryonal, pleomorphic, and alveolar. With regard to the English literature, we present the first case of alveolar rhabdomyosarcoma of the larynx ever described in a child. This tumor has been diagnosed on an endoscopic biopsy. Thus, a unilateral arytenoidectomy has been performed. This tumor has a poor prognosis. Lymph node metastases were successfully treated by chemotherapy and radiotherapy. Surgery has shifted from radical to conservative combined with adjuvant treatments.

Background: Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Anaplasia is a rare phenomenon seen in childhood RMS. The most common histologic subtype was Embryonal followed by Alveolar and spindle subtype., Design: A total of 11 cases of pediatric RMS were selected from January 2017 to June 2019 presenting at various sites. Out of 11 cases, 2 were further diagnosed as Embryonal, 2 as Alveolar, 2 as Pleomorphic, 1 as Spindle subtype and rest 4 as RMS-NOS based on morphology. All cases were positive for Desmin. The presence of cells with lobated, hyperchromatic nuclei at least three times larger than the tumor cell (anaplastic cells) was selected as the main criterion to diagnose Anaplasia., Results: Out of the total 11 cases, anaplasia was seen in 7 cases. Out of these seven, five cases showed Focal Anaplasia (FA) (71.4%) and 2 cases showed Diffuse Anaplasia (DA) (28.6%). Out of 2 cases of Embryonal RMS one exhibited focal anaplasia (50%). One case of Spindle RMS showed diffuse anaplasia, 2 cases of pleomorphic RMS showed focal anaplasia. Out of 3 cases of RMS- NOS, 2 exhibited focal anaplaisa and one displayed Diffuse anaplasia. Both Alveolar RMS had no features of anaplasia., Conclusion: Presence of Anaplasia is a frequent observation in pediatric RMS. Anaplasia is often under reported in pediatric RMS. Pathologist should be more aware of this rare phenomenon., Competing Interests: None

Background: The possible application of gene fusion transcripts as tumor-specific noninvasive liquid biopsy biomarkers was investigated in blood plasma from patients with alveolar rhabdomyosarcoma (ARMS) and synovial sarcoma (SS)., Methods: Patients entered in the CWS Soft-Tissue Sarcoma Registry (SoTiSaR) with tumors positive for fusion genes and available blood/plasma samples were included in our analysis. Cell-free exosomal RNA was extracted and used to detect PAX-FOXO1 or SYT-SSX fusion transcripts by reverse transcription quantitative PCR (RT-qPCR)., Results: The analysis included 112 ethylene diamine tetraacetic acid blood samples from 80 patients (65 with ARMS, 15 with SS; 34 with localized, 46 with metastatic disease). For patients with metastatic ARMS, 62% (n = 18) of initial liquid biopsies were positive, and 16 (89%) of them showed initial bone marrow (BM) metastases. For all patients with primary localized ARMS, liquid biopsy was negative at diagnosis. Of the 48 plasma samples collected during therapy and follow-up, five were positive. None of the liquid biopsies from patients with SS were positive., Conclusions: This liquid biopsy assay based on the detection of fusion transcripts in cell-free RNA from blood exosomes is suitable for analysis of patients with ARMS. Results showed good correlation with the initial tumor status; liquid biopsy was positive in 94% of patients with metastatic ARMS and initial BM involvement, whereas biopsies from all patients with localized tumors were negative. Prospective validation and optimization of the assay, as well as its application for other markers in diagnostics and monitoring of soft-tissue sarcoma, are ongoing., (© 2022 Wiley Periodicals LLC.)

Abstract: Rhabdomyosarcoma (RMS) rarely arises as a primary skin tumor. It is also very rare in older adults, especially the alveolar type. We report an 80-year-old White woman who presented with a painful, erythematous, raised lesion (2 × 3.5 cm) above the left knee that was fixed within the skin, yet mobile about underlying soft tissue. A punch biopsy showed monotonous malignant round blue cells involving the dermis. Immunostains showed diffuse expression of CD56, focal chromogranin, focal dot-like pancytokeratin, CK7, and neurofilament, but negative for synaptophysin, CK20, SOX-10, MUM-1, CD43, TTF-1, and CD99. A CK20-negative variant of Merkel cell carcinoma was initially favored, but given the unusual immunophenotype and the presence of cellular dyscohesion, desmin and myogenin stains were performed, both of which were diffusely positive. Molecular testing revealed rearrangement of PAX3 and FOXO1 loci, confirming the diagnosis of alveolar RMS. PET/CT showed a probable 1.9-cm left inguinal lymph node metastasis; no internal or deep soft tissue primary tumor mass was identified, supporting a true primary cutaneous origin. Alveolar RMS may express keratins and neuroendocrine markers, making it easy to confuse with Merkel cell carcinoma on those exceptionally rare instances, when it arises in the skin of older adults., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

PAX3/7-FOXO1 fusion-negative alveolar rhabdomyosarcoma (ARMS) developed in a patient presenting with intellectual disability and dysmorphic facial features. Whole exome sequencing analysis of a germline sample identified a PACS1 c.607 C>T de novo variant and the patient was diagnosed with Schuurs-Hoeijmakers syndrome (SHS). SHS is a rare disease characterized by intellectual disability and dysmorphic facial features, among various physical abnormalities, due to PACS1 c.607 C>T de novo variant. Due to the rarity of the SHS, diagnosis based on phenotypic information is difficult. To date, there have been no previous reports describing malignancy associated with SHS. Comprehensive somatic mutation analysis revealed a unique pattern of genetic alterations in the PAX3/7-FOXO1 fusion-negative ARMS tumor, including mutations in the oncogene, HRAS; MYOD1, a molecule essential for muscle differentiation; and KMT2C and TET1, genes encoding factors involved in epigenetic regulation. Although the role of PACS1 in tumorigenesis is unclear, it is reported to function in apoptosis regulation. Our case suggests that PACS1 could have a novel role in oncogenesis., (© 2021. The Author(s), under exclusive licence to The Japan Society of Human Genetics.)

Alveolar rhabdomyosarcoma (ARMS) is associated with PAX3/PAX7-FOXO1 fusion, which confers specific clinic and biologic characteristics with inferior outcomes. A minority of tumors still histologically classified as "true" ARMS lack the canonical PAX-FOXO1 fusion but have new molecular alterations. We present the first case of PAX3-NCOA1 ARMS with clinical data and follow-up in a two-year-old girl with ARMS of the tongue and nodal extension, treated with chemotherapy, hemi glossectomy, lymph node dissection, and brachytherapy to conserve oral function and limit long-term sequelae. Given the rarity of such variant fusion in ARMS, international collaboration is required to evaluate its prognostic value., (© 2021 The Authors. Pediatric Blood & Cancer published by Wiley Periodicals LLC.)

Alveolar rhabdomyosarcoma (ARMS) commonly occurring in children and adolescents, is a rare and aggressive soft tissue malignancy demonstrating rapid growth and dissemination. Although their histopathologic and immunohistochemical findings are well known, cytomorphological features on serous effusions have not been well documented. A case of metastatic rhabdomyosarcoma diagnosed on cytological examination of the pericardial fluid cytology and discuss the diagnostic difficulties that were encountered in this case has been presented., (© 2021 Wiley Periodicals LLC.)

Alveolar rhabdomyosarcoma (ARMS) is a highly aggressive subtype of childhood cancer for which efficacious treatments are needed. Immunotherapy represents a new therapeutic opportunity to pursue, but it requires the identification of worthwhile tumor antigens. Herein, we exploited the capacity of ARMS autoantibodies to recognize tumor self-antigens, probing human protein microarrays with plasma from ARMS patients and healthy subjects. We assessed the autoantibody response in ARMS, validated data with independent techniques, and estimated autoantibodies diagnostic and prognostic significance by receiver-operator characteristic curves (ROC), uni- and multivariate analysis. Of the 48 tumor antigens identified, General Transcription Factor II-I (GTF2i) and Protocadherin Gamma Subfamily C5 (PCDHGC5) were selected as candidate targets to validate tumor-restricted antigen expression and autoantibody reactivity through an independent technique and wider cohort of cases. GTF2i and PCDHGC5 overexpression was observed in tumor tissues compared to normal counterparts, and anti-GTF2i and -PCDHGC5 autoantibodies were found able to distinguish ARMS patients from healthy subjects as well as cases with different histology. Moreover, low levels of PCDHGC5 autoantibodies characterized patients with worse event-free survival and proved to be an independent negative prognostic factor. This approach provided the first comprehensive autoantibody profile of ARMS, gave novel insights into the immune response of this malignancy and paved the way toward novel potential antibody-based therapeutic applications suitable to improve the survival of ARMS patients., (© 2021 The Author(s). Published with license by Taylor & Francis Group, LLC.)

Introduction: Rhabdomyosarcoma (RMS) is a malignant solid tumor of mesenchymal origin. It is the most com mon soft-tissue sarcoma in childhood and adolescence. 65% of cases are diagnosed before the age of 6. Histological subtypes include embryonal, alveolar, pleomorphic, and fused-cell RMS. The embryo nal subtype is more frequent in children, while the alveolar one is more frequent in adolescents and adults., Objective: To describe the clinical presentation of primary alveolar rhabdomyosarcoma in a schoolgirl., Clinical Case: 7-year-old schoolgirl with one-month history of progressive pain in her left thigh. X-ray shows a lytic lesion in the left femur diaphysis. A study was performed with 2 biopsies, immunohistochemistry, and PAX-FOXO1 studies which were compatible with alveolar RMS. Con clusion: Primary alveolar rhabdomyosarcoma of the bone is rare, but it should be considered within the differential diagnosis of primary small-round-blue cell bone tumors. Despite presenting a poor prognosis cytogenetic, this type of tumor seems to have better biological behavior, which for a successful treatment makes necessary to have a high index of suspicion in order to install a multimodal therapy in the context of a national protocol.

Rhabdomyosarcoma (RMS) is a mesenchymal malignancy phenocopying muscle and is among the leading causes of death from childhood cancer. Metastatic alveolar rhabdomyosarcoma is the most aggressive subtype with an 8% 5-yr disease-free survival rate when a chromosomal fusion is present and a 29% 5-yr disease-free survival rate when negative for a fusion event. The underlying biology of PAX -fusion-negative alveolar rhabdomyosarcoma remains largely unexplored and is exceedingly rare in Li-Fraumeni syndrome patients. Here, we present the case of an 11-yr-old male with fusion-negative alveolar rhabdomyosarcoma studied at end of life with a comprehensive functional genomics characterization, resulting in identification of potential therapeutic targets for broader investigation., (© 2021 Ricker et al.; Published by Cold Spring Harbor Laboratory Press.)

Involvement of serous cavity specimens by alveolar rhabdomyosarcoma (ARMS) is a rare event and only a few case reports have been reported in the literature, with conflicting cytomorphologic patterns. Herein, we report on a 41-year-old man with no significant past medical history who presented with pancytopenia and shortness of breath and was found to have widely metastatic sinonasal alveolar rhabdomyosarcoma, including involvement of the pleura. The pleural fluid specimen was cellular and contained ARMS cells in small-to-medium sized three-dimensional fragments that resembled an adenocarcinoma or mesothelioma, and numerous single cells were seen in the background. The individual tumor cells demonstrated variable morphology; all were large, with varying degree of cytoplasm, and multinucleated cells were commonly seen in the background. The cells were negative for calretinin and claudin-4 and were positive for myogenin, confirming the diagnosis. Given the cytomorphologic diversity of ARMS seen in serous fluid specimens, patient history and the use of confirmatory immunostains are essential., (© 2020 Wiley Periodicals LLC.)

Rhabdomyosarcoma (RMS) masquerading as acute leukemia (AL) is very rare. We report a case which presented as acute leukemia subsequently diagnosed to be Alveolar RMS of Urinary Bladder. Although cases of RMS with leukemic presentation have been reported, to our knowledge this is the first case of Alveolar RMS of Urinary Bladder with leukemic picture at initial presentation. We would like to emphasize that this critical error can have serious consequences on the treatment and outcome of these patients.

In this case report we evaluate the genetics of and scientific basis of therapeutic options for a 14-yr-old male patient diagnosed with metastatic PAX3-FOXO1 fusion positive alveolar rhabdomyosarcoma. A distinguishing genetic feature of this patient was a germline RET C634F mutation, which is a known driver of multiple endocrine neoplasia type 2A (MEN2A) cancer. Through sequential DNA and RNA sequencing analyses over the patient's clinical course, a set of gene mutations, amplifications, and overexpressed genes were identified and biological hypotheses generated to explore the biology of RET and coexisting signaling pathways in rhabdomyosarcoma. Somatic genetic abnormalities identified include CDK4 amplification and FGFR4 G388R polymorphism. Because of the initial lack of patient-derived primary cell cultures, these hypotheses were evaluated using several approaches including western blot analysis and pharmacological evaluation with molecularly similar alveolar rhabdomyosarcoma cell lines. Once a primary cell culture became available, the RET inhibitor cabozantinib was tested but showed no appreciable efficacy in vitro, affirming with the western blot negative for RET protein expression that RET germline mutation could be only incidental. In parallel, the patient was treated with cabozantinib without definitive clinical benefit. Parallel chemical screens identified PI3K and HSP90 as potential tumor-specific biological features. Inhibitors of PI3K and HSP90 were further validated in drug combination synergy experiments and shown to be synergistic in the patient-derived culture. We also evaluated the use of JAK/STAT pathway inhibitors in the context of rhabdomyosarcomas bearing the FGFR4 G388R coding variant. Although the patient succumbed to his disease, study of the patient's tumor has generated insights into the biology of RET and other targets in rhabdomyosarcoma., (© 2020 Crawford et al.; Published by Cold Spring Harbor Laboratory Press.)

Introduction: Alveolar rhabdomyosarcoma (RMS) usually occurs in adolescents and young adults, and most frequently arises in the extremities., Case Report: We present a rare case of metastatic alveolar RMS from a nasal primary to cervical lymph nodes (LNs) in an elderly patient, diagnosed on the fine-needle aspiration (FNA) biopsy. Smears showed malignant round cells featuring focal rhabdoid appearance, with rhabdomyoblastic differentiation further supported by immunocytochemical stains. Diagnosis of alveolar RMS was confirmed by fluorescence in situ hybridization (FISH) identifying FOXO1 gene involvement with dual colour break-apart probes at locus 13q14., Discussion: The differential diagnosis for a small round blue cell tumour in the elderly generally includes metastatic small cell carcinoma, lymphoma, malignant melanoma, RMS, desmoplastic small round cell tumour and Ewing's sarcoma/primitive neuroectodermal tumour. Subtle morphological analysis and expression pattern of immunostaining for skeletal muscle differentiation led to the diagnosis of RMS. Cytogenetic testing on the FOXO1 gene rearrangement helps definite subtyping of alveolar RMS.

Pseudoglandular schwannoma (PGS) is a rare morphological variant of benign schwannoma. PGS is quite distinct from the somewhat better characterized glandular schwannoma variant. PGS is characterized by the presence of gland-like structures lined with pseudocolumnar or cuboidal-like neoplastic Schwann cells lining variably sized cystic space cells. Herein, we describe a rare case of PGS in a 17-year-old adolescent boy with a neck mass 8.5 cm in diameter present for 2 years with a recent increase in size. Fine-needle aspiration (FNA) demonstrated abundant rhabdoid-like cuboidal cells, plasmacytoid cells, binucleation, clusters of round to oval cells with scant cytoplasm, and a lack of stromal cells with spindle or oval nuclei. These findings were challenging and were reminiscent of alveolar rhabdomyosarcoma on FNA. Magnetic resonance imaging was also suggestive of malignancy. However, the histologic picture and the immunohistochemical analysis of the resected mass were consisted with PGS. The numerous rhabdoid-like cuboidal neoplastic Schwann cells with a plasmacytoid appearance, paving cystic spaces, and the lack of blunt-ended proliferating stromal cells on smears mimicked alveolar rhabdomyosarcoma on FNA. To our knowledge, cytological features of PGS have not been previously reported. This is the first published report of an unusual PGS case located in the neck region causing a diagnostic dilemma on cytology., (© 2019 Wiley Periodicals, Inc.)

Rhabdomyosarcoma comprises about half of the soft tissue tumors. Approximately 40% of the alveolar subtype occur in the head and neck region. Patients present with unilateral nasal mass with/without lymphadenopathy and with/without orbital manifestations. Diagnosis is aided radiologically by CT scan, MRI along with biopsy and is confirmed by immunohistochemistry. Treatment involves surgical resection, chemotherapy, radiotherapy or a combination of these. In spite of treatments, however, the outcome is poor. This is a case report of 14-year-old male who presented with unilateral nasal mass with proptosis of right eye who was eventually diagnosed as a case of alveolar rhabdomyosarcoma of solid variant.

Primary cutaneous alveolar rhabdomyosarcoma is an extremely rare and highly aggressive soft tissue sarcoma that predominantly arises on the extremities and perineum of adolescents and young adults. Dermatologists should be aware of these tumors in order to promptly make the diagnosis and initiate treatment., (© 2019 Wiley Periodicals, Inc.)

We present the case of a 22-year-old woman who developed increasing headaches, nausea, and vomiting. Imaging identified a 3 × 3 cm heterogeneously enhancing cystic mass in the posterior III ventricular/pineal region. Pathology review of the initial lesion revealed a highly malignant spindle cell neoplasm composed of round to mostly oval elongated cells with relatively small amounts of cytoplasm arranged in sheets and fascicles with focal storiform pattern. Whole genome methylation analysis through unsupervised clustering with data generated from other primary intracranial tumors and peripheral sarcomas was performed at the German Cancer Research Center (DKFZ) and classified the tumor with the group of alveolar rhabdomyosarcomas (ARMS). Further RNA sequencing revealed an in frame PAX3 (EX 7)-NCOA2 (EX12) fusion confirming the diagnosis. This is the first evidence of occurrence of PAX3-NCOA2 in primary CNS ARMS., (© 2019 American Association of Neuropathologists, Inc. All rights reserved.)

Alveolar rhabdomyosarcoma (ARMS) is a nonepithelial tumor with skeletal muscle differentiation and typically affects adolescents and young adults. The cytological features of ARMS in body fluid have not been well characterized, which complicates diagnosis. Here, we describe the cytological features of ARMS in the ascites of a 50-year-old woman with an intra-abdominal mass and abundant ascites. Aspiration cytology of ascitic fluid revealed numerous small discohesive round cells with mild nuclear atypia and prominent nucleoli. Rhabdomyoblastic cells, characteristic of rhabdomyosarcoma, were identified rarely. Cannibalism and 'window' formation, as seen in reactive mesothelial cells, complicated the diagnosis of ARMS. Histological examination established the diagnosis of ARMS, which was confirmed by immunohistochemical expression of myogenic markers. When diagnosing ARMS from effusion samples, the diagnostic problems associated with the morphological similarity of ARMS cells to reactive mesothelial cells should be considered.

Objective: The study was to assess whether tumour expressions of hypoxia-inducible factor (HIF)-1α, glucose transporter (GLUT)-1, carbonic anhydrase (CA) IX and vascular endothelial growth factor (VEGF) predict response to neo-adjuvant chemotherapy (naCHT) in children with inoperable rhabdomyosarcoma (RMS). Methods: Immunohistochemical expressions of hypoxia markers were determined semi-quantitatively in tumour tissue microarray of 46 patients with embryonal RMS (RME) and 20 with alveolar (RMA), treated with CWS protocols (1992-2013). Results: In paediatric RME, response to naCHT was influenced significantly by tumour expression of CA IX and GLUT-1. Patients with RMA with low expressions of analysed markers responded well to naCHT, while all poor-responders expressed highly hypoxia markers. Only 5.88% of RMA and 11.11% of RME tumours did not express any of the proteins. In both RME and RMA subgroups, most poor-responders demonstrated simultaneous high expression of ≥3 markers, while most patients expressing ≤2 markers responded well to naCHT. In the whole cohort, co-expression of ≥3 markers, was the only independent factor predicting poor-response to chemotherapy (odds ratio 14.706; 95% CI 1.72-125.75; p  = 0.014). Conclusions: Immunohistochemical expression pattern of four endogenous markers of hypoxia, in tumour tissue at diagnosis, emerges as a promising tool to predict response to naCHT in children with inoperable RMS.

Cell-free DNA (cfDNA), which are small DNA fragments in blood derived from dead cells including tumor cells, could serve as useful biomarkers and provide valuable genetic information about the tumors. cfDNA is now used for the genetic analysis of several types of cancers, as a surrogate for tumor biopsy, designated as "liquid biopsy." Rhabdomyosarcoma (RMS), the most frequent soft tissue tumor in childhood, can arise in any part of the body, and radiological imaging is the only available method for estimating the tumor burden, because no useful specific biological markers are present in the blood. Because tumor volume is one of the determinants of treatment response and outcome, early detection at diagnosis as well as relapse is essential for improving the treatment outcome. A 15-year-old male patient was diagnosed with alveolar RMS of prostate origin with bone marrow invasion. The PAX3-FOXO1 fusion was identified in the tumor cells in the bone marrow. After the diagnosis, cfDNA was serially collected to detect the PAX3-FOXO1 fusion sequence as a tumor marker. cfDNA could be an appropriate source for detecting the fusion gene; assays using cfDNA have proved to be useful for the early detection of tumor progression/recurrence. Additionally, the fusion gene dosage estimated by quantitative polymerase chain reaction reflected the tumor volume during the course of the treatment. We suggest that for fusion gene-positive RMSs, and other soft tissue tumors, the fusion sequence should be used for monitoring the tumor burden in the body to determine the diagnosis and treatment options for the patients., (© 2019 Wiley Periodicals, Inc.)

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and represents a high-grade neoplasm of skeletal myoblast-like cells. Decades of clinical and basic research have gradually improved our understanding of the pathophysiology of RMS and helped to optimize clinical care. The two major subtypes of RMS, originally characterized on the basis of light microscopic features, are driven by fundamentally different molecular mechanisms and pose distinct clinical challenges. Curative therapy depends on control of the primary tumour, which can arise at many distinct anatomical sites, as well as controlling disseminated disease that is known or assumed to be present in every case. Sophisticated risk stratification for children with RMS incorporates various clinical, pathological and molecular features, and that information is used to guide the application of multifaceted therapy. Such therapy has historically included cytotoxic chemotherapy as well as surgery, ionizing radiation or both. This Primer describes our current understanding of RMS epidemiology, disease susceptibility factors, disease mechanisms and elements of clinical care, including diagnostics, risk-based care of newly diagnosed and relapsed disease and the prevention and management of late effects in survivors. We also outline potential opportunities to further translate new biological insights into improved clinical outcomes.

Competing Interests: Competing interests: None declared.

Background: A small number of rhabdomyosarcoma (RMS) cases involve the bone marrow. A leukemic presentation of RMS has been reported in a few case series, although almost all cases of leukemic RMS are not completely mimicking leukemia. We encountered a case with RMS cell infiltration of the bone marrow that resembled floating hematological cells., Case Presentation: We encountered a rare case of a 15-year-old boy with a 2-week history of left femoral pain. Upon admission, he was afebrile with no other symptoms. No apparent cause of femoral pain was detected on an initial examination. Laboratory findings revealed normal white blood cell (WBC) count and hemoglobin concentration, with a platelet count of 10.3 × 10 4 /μL. WBCs included 2.0% metamyelocytes, 4.5% myelocytes, and 0.5% blasts. Lactate dehydrogenase concentration was 1299 U/L, creatine kinase was 437 U/L, and C-reactive protein was 1.25 mg/dL. Bone marrow aspiration demonstrated hypercellular marrow (nucleated cell count 1.84 × 10 4 /μL) and 89.0% of blast-like cells of all nucleated cells. The proliferating cells were negative for myeloperoxidase and esterase, and strongly positive for CD56. Positron emission tomography exhibited extensive accumulation of 18 F-fludeoxyglucose with a SUVmax of 7.09. Magnetic resonance imaging revealed T1-low intensity, gadolinium-enhanced, diffuse, and irregular lesions on his pelvis and bilateral femurs. These laboratory and imaging findings suggested hematological malignancy with diffuse bone involvement, suggestive of acute leukemia. However, the pathological diagnosis of bone marrow and basal penile muscle biopsy was alveolar RMS. Karyotype analysis of bone marrow cells revealed the characteristic translocation of t(2;13)(q35;q14). The final diagnosis was alveolar RMS with massive involvement of the bone marrow and the primary site in the perineal muscles. The tumor cells both of the primary site and bone marrow were positive for myogenin., Conclusions: A literature review found a misdiagnosed case of completely mimicking leukemic RMS as natural-killer (NK)-cell leukemia. Such a misdiagnosis can have critical consequences. We experienced a rare case of alveolar RMS with symmetrical diffuse bone marrow involvement completely masquerading as acute leukemia. The results of a surface marker study showing that the tumor cells had a near NK-cell phenotype were misleading.

Subsets of primitive round-cell sarcomas remain difficult to diagnose and classify. Among these is a rare round-cell sarcoma that harbors a CIC gene rearrangement known as CIC-rearranged undifferentiated round-cell sarcoma, which is most commonly fused to the DUX4 gene. Owing to its aggressive clinical behavior and potential therapeutic implications, accurate identification of this novel soft tissue sarcoma is necessary. Definitive diagnosis requires molecular confirmation, but only a few centers are as yet able to perform this test. Several studies have shown that PEA3 subfamily genes, notably ETV4 (belonging to the family of ETS transcription factors), are upregulated in CIC-rearranged undifferentiated round-cell sarcomas. We performed a detailed immunohistochemical analysis to investigate ETV4 expression in CIC-rearranged undifferentiated round-cell sarcomas and their potential mimics (especially Ewing sarcomas). The study cohort included 17 cases of CIC-rearranged undifferentiated round-cell sarcomas, and 110 tumors that morphologically mimic CIC-rearranged undifferentiated round-cell sarcomas: 43 Ewing sarcomas, 25 alveolar rhabdomyosarcomas, 20 poorly differentiated round-cell synovial sarcomas, 10 desmoplastic round-cell tumors, 5 BCOR-CCNB3 sarcomas, 5 lymphoblastic lymphomas, and 2 rhabdoid tumors. All CIC-rearranged undifferentiated round-cell sarcomas (on core needle biopsies and open biopsies) were ETV4-positive with a strong diffuse nuclear pattern. Among the other 110 tumors, only six cases (four Ewing sarcomas, one alveolar rhabdomyosarcoma, and one desmoplastic round-cell tumor) showed focal (<5% of tumor cells) and very weak nuclear expression of ETV4; all other tumors were completely negative for ETV4. We conclude that systematic immunohistochemical analysis of ETV4 makes it possible to diagnose undifferentiated round-cell sarcomas (with no molecular markers for sarcoma-associated translocation) such as CIC-rearranged undifferentiated round-cell sarcoma.

Fluorescence in situ hybridization (FISH) for FOXO1 gene rearrangement and reverse transcription-polymerase chain reaction (PCR) for PAX3/7-FOXO1 fusion transcripts have become routine ancillary tools for the diagnosis of alveolar rhabdomyosarcomas (ARMS). Here we summarize our experience of these adjunct diagnostic modalities at a tertiary center, presenting the largest comparative series of FISH and PCR for suspected or possible ARMS to date. All suspected or possible ARMS tested by FISH or PCR for FOXO1 rearrangement or PAX3/7-FOXO1 fusion transcripts over a 7-year period were included. FISH and PCR results were correlated with clinical and histologic findings. One hundred samples from 95 patients had FISH and/or PCR performed. FISH had higher rates of technical success (96.8 %) compared with PCR (88 %). Where both tests were utilized successfully, there was high concordance rate between them (94.9 %). In 24 histologic ARMS tested for FISH or PCR, 83.3 % were translocation-positive (all for PAX3-FOXO1 by PCR) and included 3 histologic solid variants. In 76 cases where ARMS was excluded, there were 3 potential false-positive cases with FISH but none with PCR. PCR had similar sensitivity (85.7 %) and better specificity (100 %) in aiding the diagnosis of ARMS, compared with FISH (85 and 95.8 %, respectively). All solid variant ARMS harbored FOXO1 gene rearrangements and PAX3-FOXO1 ARMS were detected to the exclusion of PAX7-FOXO1. In comparative analysis, both FISH and PCR are useful in aiding the diagnosis of ARMS and excluding its sarcomatous mimics. FISH is more reliable technically but has less specificity than PCR. In cases where ARMS is in the differential diagnosis, it is optimal to perform both PCR and FISH: both have similar sensitivities for detecting ARMS, but FISH may confirm or exclude cases that are technically unsuccessful with PCR, while PCR can detect specific fusion transcripts that may be useful prognostically.

Introduction: Alveolar rhabdomyosarcomas of the mediastinum in children are rarely reported. Multimodality therapy including chemotherapy, surgery and radiotherapy make up the backbone of the treatment of childhood rhabdomyosarcomas. Complete resection whenever achievable is an important prognostic factor. However, complete resection of tumors in the mediastinum often poses a unique challenge to thoracic surgeons due to their close proximity to important neurovascular structures. Complete resection may not always be possible and judicious peri-operative planning and preparation are required to avoid creating unnecessary surgical morbidities resulting in delay of adjuvant therapy., Case Presentation: A 4-month-old Chinese baby boy was presented to our hospital with stridor, shortness of breath and episodes of cyanosis. Imaging studies found an anterior mediastinal mass compressing the trachea and other neurovascular structures and he was diagnosed to have alveolar rhabdomyosarcoma. Our patient received upfront chemotherapy and subsequently open resection of the mass was attempted via median sternotomy. Intraoperatively, the mass had invaded into the great vessels, precluding a complete resection. Debulking surgery was performed instead and our patient received timely postoperative chemoradiotherapy., Conclusions: We report a rare case of childhood alveolar rhabdomyosarcoma of the mediastinum with vascular invasion treated with chemoradiotherapy and debulking surgery. Complete resection was not possible due to the close proximity to the great vessels. Different surgical approaches to the mediastinum have been reported in adults and children alike. Regardless of the surgical access, the treatment of childhood rhabdomyosarcomas should be individualized, with careful balance between surgical clearance and surgical morbidity.

A 3-year-old child presented with a history of conjunctivitis in her OS. She had hyperglobus of the OS and a palpable mass in the left inferior orbit. An urgent MRI revealed an enhancing mass in the left orbit. The patient underwent an incisional biopsy with pathologic assessment most consistent with embryonal rhabdomyosarcoma. However, subsequent molecular genetic testing of the biopsy specimen was positive for the PAX3/PAX7-FKHR chimeric gene, indicating the tumor was actually an alveolar rhabdomyosarcoma. The patient received a more intensive chemotherapy regimen and also was treated with proton-beam radiotherapy. After chemotherapy and proton irradiation, the patient's tumor shrank considerably, and she remained in remission at over 3 years of follow up. This patient illustrates the new tools at the disposal of the orbital specialist including molecular genetic testing and proton-beam irradiation to diagnose and treat orbital rhabdomyosarcoma.