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Purpose The histological response to neoadjuvant chemotherapy is an important prognostic factor in patients with osteosarcoma (OS) and Ewing sarcoma (EWS). The aim of this study was to assess baseline primary tumour FDG uptake on PET/CT, and serum values of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH), to establish whether these factors are correlated with tumour necrosis and prognosis. Methods Patients treated between 2009 and 2014 for localized EWS and OS, who underwent FDG PET/CT as part of their staging work-up, were included. The relationships between primary tumour SUVmax at baseline (SUV1), SUVmax after induction chemotherapy (SUV2), metabolic response calculated as [(SUV1 − SUV2)/SUV1)] × 100, LDH and ALP and tumour response/survival were analysed. A good response (GR) was defined as tumour necrosis >90 % in patients with OS, and grade II-III Picci necrosis (persitence of microscopic foci only or no viable tumor) in patients with Ewing sarcoma. Results The study included 77 patients, 45 with EWS and 32 with OS. A good histological response was achieved in 53 % of EWS patients, and 41 % of OS patients. The 3-year event-free survival (EFS) was 57 % in EWS patients and 48 % OS patients. The median SUV1 was 5.6 (range 0 – 17) in EWS patients and 7.9 (range 0 – 24) in OS patients ( p  = 0.006). In EWS patients the GR rate was 30 % in those with a high SUV1 (≥6) and 72 % in those with a lower SUV1 ( p  = 0.0004), and in OS patients the GR rate was 29 % in those with SUV1 ≥6 and 64 % in those with a lower SUV1 ( p  = 0.05). In the univariate analysis the 3-year EFS was significantly better in patients with a low ALP level (59 %) than in those with a high ALP level (22 %, p  = 0.02) and in patients with a low LDH level (62 %) than in those with a high LDH level (37 %, p  = 0.004). In EWS patients the 3-year EFS was 37 % in those with a high SUV1 and 75 % in those with a low SUV1 ( p  = 0.004), and in OS patients the 3-year EFS was 32 % in those with a high SUV1 and 66 % in those with a low SUV1 ( p  = 0.1). Histology, age and gender were not associated with survival. In the multivariate analysis, SUV1 was the only independent pretreatment prognostic factor to retain statistical significance ( p  = 0.017). SUV2 was assessed in 25 EWS patients: the median SUV2 was 1.9 (range 1 – 8). The GR rate was 20 % in patients with a high SUV2, and 67 % in those with a low SUV2 ( p  = 0.02). A good metabolic response (SUV reduction of ≥55 %) was associated with a 3-year EFS of 80 % and a poor metabolic response with a 3-year EFS of 20 % ( p  = 0.05). In the OS patients the median SUV2 was 2.7 (range 0 – 4.5). Neither SUV2 nor the metabolic response was associated with outcome in OS patients. Conclusion FDG PET/CT is a useful and noninvasive tool for identifying patients who are more likely to be resistant to chemotherapy. If this finding is confirmed in a larger series, SUV1, SUV2 and metabolic response could be proposed as factors for stratifying EWS patients to identify those with high-grade localized bone EWS who would benefit from risk-adapted induction chemotherapy.

Ewing sarcoma (ES) is the second most common primary malignant bone tumour in children and adolescents. About 14.5% of primary malignancies develop in pelvic bones, where they typically have worse prognoses than extremity or acral sarcomas. It usually presents with aggressive features on radiology scans, but may also present with different radiological characteristics. In this series, we describe rare appearances of pelvic skeletal Ewing sarcoma, with large extraosseous cystic component on imaging, defined by the presence of fluid-filled spaces in the extraosseous tumour lesion, which distinguishes it from the solid nature of conventional ES. We report 3 cases of cystic presentation of ES, with imaging features supporting diagnosis of a primary malignant bone tumour arising from the superior pubic ramus with associated massive intrapelvic solid and cystic mass. CT-guided biopsy provided diagnosis of ES, with large intrapelvic soft tissue and cystic component. These patients underwent neo-adjuvant chemotherapy and proton beam therapy with significant reduction in size of the solid components, while the cystic components remained relatively unchanged. Two patients underwent surgical resection of the tumour (navigated P3 internal hemipelvectomy and hemipelvis P2/P3 resection, respectively), and one patient died while on treatment. In both who underwent surgery, histology showed ES with margins clear and more than 99% of treatment-induced necrosis. To the authors’ knowledge, this unusual presentation of pelvic ES is described for the first time in the literature as a case series, with particular reference to atypical extraosseous cystic changes, along with the clinical and radiological characteristics, and their treatment.

Primary intraarticular sarcomas are rare. We describe a unique case of intraarticular Ewing sarcoma arising in Hoffa fat pad of knee in a woman. The patient was treated successfully with chemotherapy and left knee arthroplasty; however, the tumor recurred after 3 years.We review the literature on primary intraarticular sarcomas and Hoffa fat pad masses in the knee.

ObjectivePre-operative whole-bone MRI is required to assess intra-osseous tumour extent and to identify skip metastases in cases of bone sarcoma. The current study aims to determine the sensitivity, specificity, and diagnostic accuracy of whole-bone MRI for the identification of skip metastases.Materials and methodReview of 162 patients with long bone osteosarcoma or Ewing sarcoma who had undergone whole-bone MRI to assess intra-osseous tumour length and identify skip metastases. Comparison was made with post-chemotherapy MRI to look for a change in the appearance of suspected skip metastases, and resection specimens were assessed for the presence of skip metastases. The presence of local osseous recurrence was determined at final follow-up.ResultsThere were 112 males and 50 females (mean age 18.8 years), with 119 osteosarcomas and 43 Ewing sarcomas. Skip metastases were diagnosed on whole-bone MRI in 23 cases (14.2%). In 2 cases, pre-operative needle biopsy diagnosed enchondromata, resulting in false positive diagnoses. Skip metastases were diagnosed in the resection specimens in 3 cases, and based on comparison with post-chemotherapy MRI in 12. There was no evidence of local osseous recurrence in 160 patients, while late recurrence occurred in 2 patients. Sensitivity was calculated as 88.2%, specificity as 97.6%, and diagnostic accuracy as 96.7%.ConclusionWhole-bone MRI has a high sensitivity, specificity, and diagnostic accuracy for the identification of skip metastases in osteosarcoma and Ewing sarcoma. The possibility of false positive skip lesions and late local osseous recurrence is also highlighted.

Background Sarcopenia is an indicator of negative outcomes in many diseases in adults. Reports indicate this might also be true in children. Objective To evaluate the effect of sarcopenia and sarcopenic obesity on event-free survival (EFS) and overall survival (OS) in children with Ewing sarcoma and osteosarcoma. Materials and methods We retrospectively measured total muscle areas of the pectoralis, paraspinal (T12 level) and psoas (L4 level) muscles and total abdominal muscle area (L3 level) on computed tomography images in 60 children diagnosed with either Ewing sarcoma ( n  = 34) or osteosarcoma ( n  = 26). Skeletal muscle indices (SMI) were calculated by normalizing muscle area to patient height. Vertebral morphologic parameters of T12 and L4 vertebrae were measured and correlated to patient height to use as a substitute in cases of missing height data (SMI T12 and SMI L4 ). We calculated sarcopenic obesity index by dividing SMI by body mass index. We subdivided children into two groups according to the median value of each parameter and assessed the differences in survival between the groups. Results No skeletal muscle index or sarcopenic obesity index parameter significantly affected event-free or overall survival in the total group analysis. In the non-metastatic group, higher values of SMI–paraspinal and SMI T12 –psoas were correlated with longer event-free survival and no patient died in this group. Boys and children in the metastatic group with higher SMI T12 –paraspinal values had significantly longer event-free survival and both event-free and overall survival, respectively. Conclusion Although some parameters were correlated with event-free and overall survival, neither sarcopenia nor sarcopenic obesity were reliably associated with survival in children with Ewing sarcoma or osteosarcoma.

Improved understanding of tumor biology through molecular alteration and genetic advances has resulted in a number of major changes in the 2020 World Health Organization’s (WHO) classification of bone tumors. These changes include the reclassification of the existing tumors and the introduction of several new entities. A new chapter on undifferentiated small round cell sarcomas of bone and soft tissue was added to classify Ewing sarcoma and the family of Ewing-like sarcomas, which share similar histologies but different molecular and clinical behaviors. Knowledge of the current classification of bone tumors is essential to ensure the appropriate recognition of the inherent biological potential of individual osseous lesions for optimal treatment, follow-up, and overall outcome. This article reviews the major changes to the 2020 WHO’s classification of primary bone tumors and the pertinent imaging of selected tumors to highlight these changes.

Microwave ablation has been widely accepted in treating bone tumor. However, its procedure is time-consuming and usually results in postoperative fractures. To solve this problem, we designed and fabricated titanium plates customized to the patients’ bone structures. The personalized titanium plates were then used for fixation after the removal of tumorous tissue. Specifically, 3D models of tumor-bearing bone segments were constructed by using computed tomography (CT) and magnetic resonance imaging (MRI). The 3D models were used to design the personalized titanium plates. The plate model was transferred into a numerical control machine for manufacturing the personalized titanium plates by 3D printing. The plates were then surgically implanted for reconstruction assistance following microwave-induced hyperthermia to remove the bone tumor. Implementation parameters and knee functions were then evaluated. No postoperative fractures, implant failures or loosening problems occurred; mean Musculoskeletal Tumor Society score was 27.17 from the latest follow-up. Mean maximum flexion of affected knees was 114.08°. The results of knee gait analysis were comparable with normal population data. Our work suggests that personalized titanium plates can significantly improve the clinical outcomes in the surgical removal of bone tumor. This study represents the first-time effort in using personalized titanium plates for such surgery.

Back pain and syncope are two common complaints encountered in the emergency department. However, prolonged atraumatic back pain in a pediatric patient should always be considered a “red flag” symptom. We describe a case of a 14-year-old female who presented to the emergency department with syncope and hypotension due to low back pain who was ultimately diagnosed with Primary Ewing's Sarcoma (ES) of the lumbar spine with extensive pulmonary metastasis. The diagnosis was expedited by the use of a bedside RUSH exam that identified an otherwise asymptomatic, unilateral pleural effusion. ES is the second most common primary bone malignancy in adolescents and young adults and unfortunately has a delayed diagnosis due to vague and non-specific symptoms. Survival rates of metastatic ES are still quite poor despite advances in therapies and treatments. This case emphasizes the importance of obtaining a focused history and physical exam, and how targeted point-of-care ultrasonography can aid in the diagnosis of rare and life-threatening conditions.

Objective. To determine if osteosarcoma (OS) and Ewing sarcoma (EWS) of the pelvis based on MRI can be differentiated using radiomic analysis. Materials and Methods. In this study, 3.0 T magnetic resonance (MR) data of 66 patients (40 males and 26 females, mean age 27.6±13.9 years) with pathologically confirmed OS or EWS of the pelvis (35 with OS and 31 with EWS) taken from April 2013 to December 2017 were retrospectively reviewed. T2-weighted fat-saturated (T2-FS) and contrast-enhanced T1-weighted (CET1) images were manually segmented, and imaging features were extracted. Independent-sample t-test, Spearman’s test, and the least absolute shrinkage and selection operator (LASSO) method were used to select the most useful features from the original data set. The performance of radiomic analysis was investigated by the area under the receiver operating characteristic (ROC) curve (AUC) analysis. Results. 385 initial features were extracted from T2-FS and CET1 MR data. Nine features from T2-FS and 7 features from CET1 were selected by using the LASSO method. The radiomic analysis to differentiate OS and EWS of the pelvis based on T2-FS and CET1 images using the aforementioned selected features achieved AUC values of 0.881 (95% confidence interval (CI): 0.799–0.963) and 0.765 (95% CI: 0.652–0.878), respectively. Conclusion. Radiomic analysis showed potential in differentiating OS from EWS of the pelvis, in which T2-FS demonstrated better diagnostic value. To differentiate OS from EWS of the pelvis using our multiparametric MRI-based radiomic analysis could preoperatively improve diagnostic accuracy and greatly contribute to therapy planning.