[Detection of MDM2 gene amplification by fluorescence in situ hybridization and its diagnostic value in low-grade osteosarcoma].

Objective: To investigate the diagnostic value of detecting MDM2 gene amplification by fluorescence in situ hybridization (FISH) in low-grade osteosarcoma (LGOS). Methods: Thirty cases of parosteal osteosarcoma (POS) and 14 cases of low-grade central osteosarcoma (LGCOS) from April 2009 to August 2022 at Beijing Jishuitan Hospital, Capital Medical University were analyzed for the presence of MDM2 gene amplification by FISH. Fifty-eight additional cases were used as negative controls (including 28 cases of fibrous dysplasia, 5 cases of giant cell tumor, 4 cases of conventional osteosarcoma, 2 cases each of periosteal osteosarcoma, reparative changes after fracture, pleomorphic undifferentiated sarcoma, low grade myofibroblastic sarcoma, fibrous dysplasia with malignant transformation, one case each of leiomyosarcoma, sclerosing epithelioid fibrosarcoma, malignant peripheral nerve sheath tumor, desmoplastic fibroma of bone, solitary fibrous tumor, aneurysmal bone cyst, clear cell chondrosarcoma, osteofibrous dysplasia, and 3 cases of unclassified spindle cell tumor). Results: Among the 30 patients with POS, 15 were male and 15 were female, ranging in age from 10 to 59 years (mean 35 years, median 30.5 years). Among the 14 patients with LGCOS, four were male and 10 were female, ranging in age from 15 to 56 years (mean 37 years, median 36 years). All except one case were successfully detected by FISH. MDM2 gene amplification was detected in 27 cases of POS (27/29,91.3%) and 8 cases of LGCOS (8/14). All the negative controls were negative for MDM2 gene amplification. The positive rate of MDM2 gene amplification was significantly different between the case group and the control group (P<0.05). The sensitivity and specificity of MDM2 gene amplification in diagnosing POS and LGCOS were 91.3% and 100.0%; and 57.1% and 100.0%, respectively. The sensitivity and specificity of MDM2 gene amplification in diagnosing LGOS (including POS and LGCOS) were 81.3% and 100.0%, respectively. In cases where MDM2 gene was amplified, the MDM2 amplified signal was clustered. Nine cases showed increased CEP12 signal different from polyploidy which was displayed as small and weak signal points or cloud flocculent and cluster signals. Conclusions: Detection of MDM2 gene amplification by FISH is a highly sensitive and specific marker for LGOS. The interpretation criteria for FISH detection of MDM2 amplification are currently not unified. The signal characteristics need more attention when interpreting.

FGF23 Expression Is a Promising Immunohistochemical Diagnostic Marker for Undifferentiated Pleomorphic Sarcoma of Bone (UPSb).

Background: Undifferentiated pleomorphic sarcoma of bone (UPSb) is a rare primary bone sarcoma that lacks a specific line of differentiation. Distinguishing between UPSb and other malignant bone sarcomas, including dedifferentiated chondrosarcoma and osteosarcoma, is challenging due to their overlapping features. We have previously identified that UPSb tumours have elevated mRNA levels of Fibroblast Growth Factor 23 (FGF23) transcripts compared to other sarcomas including osteosarcoma. In the present study, we evaluated the specificity and practicality of FGF23 immunoreactivity as a specific diagnostic tool to differentiate UPSb tumours from osteosarcomas and dedifferentiated chondrosarcomas. Methods: A total of 10 UPSb, 10 osteosarcoma, and 10 dedifferentiated chondrosarcoma cases (all high-grade), were retrieved and immunohistochemistry for FGF23 was performed. Results: FGF23 protein was expressed at high levels in 80-90% of undifferentiated pleomorphic sarcoma of the bone cases, whereas it was expressed at significantly lower levels in dedifferentiated chondrosarcoma and osteosarcoma cases. A semiquantitative analysis, considering the intensity of immunoreactivity, confirmed significantly elevated FGF23 expression levels in UPSb tissues compared to those observed in osteosarcoma and dedifferentiated chondrosarcoma tissues. Conclusions: The results we present here suggest that FGF23 immunohistochemistry may be a useful tool to aid in differentiating UPSb from morphologically similar malignant bone sarcomas, especially in situations where sampling is restricted and there is limited clinical information available.

Integrating artificial intelligence in osteosarcoma prognosis: the prognostic significance of SERPINE2 and CPT1B biomarkers.

The principal aim of this investigation is to identify pivotal biomarkers linked to the prognosis of osteosarcoma (OS) through the application of artificial intelligence (AI), with an ultimate goal to enhance prognostic prediction. Expression profiles from 88 OS cases and 396 normal samples were procured from accessible public databases. Prognostic models were established using univariate COX regression analysis and an array of AI methodologies including the XGB method, RF method, GLM method, SVM method, and LASSO regression analysis. Multivariate COX regression analysis was also employed. Immune cell variations in OS were examined using the CIBERSORT software, and a differential analysis was conducted. Routine blood data from 20,679 normal samples and 437 OS cases were analyzed to validate lymphocyte disparity. Histological assessments of the study's postulates were performed through immunohistochemistry and hematoxylin and eosin (HE) staining. AI facilitated the identification of differentially expressed genes, which were utilized to construct a prognostic model. This model discerned that the survival rate in the high-risk category was significantly inferior compared to the low-risk cohort (p < 0.05). SERPINE2 was found to be positively associated with memory B cells, while CPT1B correlated positively with CD8 T cells. Immunohistochemical assessments indicated that SERPINE2 was more prominently expressed in OS tissues relative to adjacent non-tumorous tissues. Conversely, CPT1B expression was elevated in the adjacent non-tumorous tissues compared to OS tissues. Lymphocyte counts from routine blood evaluations exhibited marked differences between normal and OS groups (p < 0.001). The study highlights SERPINE2 and CPT1B as crucial biomarkers for OS prognosis and suggests that dysregulation of lymphocytes plays a significant role in OS pathogenesis. Both SERPINE2 and CPT1B have potential utility as prognostic biomarkers for OS.

Telangiectatic osteosarcoma in four dogs: Cytologic, histopathologic, cytochemical, and immunohistochemical findings.

Telangiectatic osteosarcoma is a rare variant of osteosarcoma histologically and clinically similar to hemangiosarcoma (HSA). This case series describes the imaging and cytologic features of four histologically confirmed telangiectatic osteosarcomas, including the use of cytochemical stains. Alkaline phosphatase (ALP) was applied to Wright-Giemsa-stained cytology slides, and Factor VIII immunohistochemistry was evaluated. Cytologic characteristics included atypical mesenchymal cells with evidence of acute and chronic hemorrhage. Telangiectatic osteosarcoma cases had positive ALP cytochemical staining, while control HSA cases were negative. Factor VIII immunohistochemistry was negative in telangiectatic osteosarcoma and positive in HSA. Cytologic diagnosis of telangiectatic osteosarcoma with positive ALP cytochemical staining can help differentiate this neoplasm from HSA.

Osteosarcoma of the wing in a sulfur-crested cockatoo.

A 26-year-old female sulfur-crested cockatoo (Cacatua galerita) was evaluated for vocalizing through the night and extending her right wing. Physical examination revealed a large, firm mass extending from the humerus to the distal aspect of the elbow. Computed tomography confirmed a large aggressive mass of the right distal humerus with a large soft tissue component, severe osteolysis, and adjacent periosteal proliferation. Fine-needle aspirates of the mass were most compatible with sarcoma, and osteosarcoma was prioritized. An unstained slide was treated with nitroblue tetrazolium chloride/5-bromo-4-chloro-3-indolyl phosphate toluidine salt-phosphatase (NBT/BCIP) substrate for ALP detection and was strongly positive, confirming a diagnosis of osteosarcoma. A month later, the patient underwent wing amputation and arrested during recovery from anesthesia. Post-mortem examination and histopathology were consistent with osteosarcoma. This case report highlights a rare occurrence of osteosarcoma in a cockatoo as well as its cytologic and histologic features. Additionally, this report provides support for NBT/BCIP application in ALP-expressing tumors, a cytochemical stain that has been minimally investigated in avian species.

Artificial neural network-based gene screening and immune cell infiltration analysis of osteosarcoma feature.

BACKGROUND: The present study aimed to construct an artificial neural network (ANN) model that leverages characteristic genes associated with osteosarcoma (OS) to enable accurate prognostication for OS patients. METHODS: Our research revealed 467 differentially expressed genes (DEGs) via gene expression contrast analysis, consisting of 345 downregulated genes and 122 upregulated genes. Gene Ontology (GO) enrichment analysis illuminated functions primarily encompassing T-cell activation, secretory granule lumen and antioxidant activity, among others. Through Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, we discovered significant correlations between the DEGs and certain pathways, including phagosome, Staphylococcus aureus infection and human T-cell leukemia virus 1 infection. We then screened out 30 characteristic DEGs (CDEGs) based on random forest analysis and constructed the ANN model using the gene score matrix. To verify the credibility and accuracy of the ANN model, we performed internal and external validation processes, which affirmed our model's predictive capabilities. RESULTS: The study further delved into the analysis of immune cell infiltration and its correlation with the target CDEGs, revealing disparities in the infiltration of 22 types of immune cells across different groups and their interrelationships. Moreover, we probed the expression of the two foremost CDEGs (YES1 and MFNG) in OS and normal tissues. We noted a positive relationship between the expression of YES1 and MFNG in OS tissues and the clinicopathological characteristics of OS patients. CONCLUSIONS: Collectively, the findings of the present study validate the effectiveness of the CDEGs-based ANN model in predicting OS patients, which might facilitate early diagnosis and treatment of OS.

Manual and Semi-Automated Measurement and Calculation of Osteosarcoma Treatment Effect Using Whole Slide Image and Qupath.

INTRODUCTION: In osteosarcoma, the most significant indicator of prognosis is the histologic changes related to tumor response to preoperative chemotherapy, such as necrosis. We have developed a method to measure the osteosarcoma treatment effect using whole slide image (WSI) with an open-source digital image analytical software Qupath. MATERIALS AND METHODS: In Qupath, each osteosarcoma case was treated as a project. All H&E slides from the entire representative slice of osteosarcoma were scanned into WSIs and imported into a project in Qupath. The regions of tumor and tumor necrosis were annotated, and their areas were measured in Qupath. In order to measure the osteosarcoma treatment effect, we needed to calculate the percentage of total necrosis area over total tumor area. We developed a tool that can automatically extract all values of tumor and necrosis areas from a Qupath project into an Excel file, sum these values for necrosis and whole tumor respectively, and calculate necrosis/tumor percentage. CONCLUSION: Our method that combines WSI with Qupath can provide an objective measurement to facilitate pathologist's assessment of osteosarcoma response to treatment. The proposed approach can also be used for other types of tumors that have clinical need for post-treatment response assessment.

Tumor microenvironment phenotypes and prognostic evaluation tools for osteosarcoma characterized by different prognostic outcomes and immunotherapy responses.

BACKGROUND: The physiological and immunological characteristics of the tumor microenvironment (TME) have a profound impact on the effectiveness of immunotherapy. The present study aimed to define the TME subtype of osteosarcoma according to the signatures representing the global TME of the tumor, as well as create a new prognostic assessment tool to monitor the prognosis, TME activity and immunotherapy response of patients with osteosarcoma. METHODS: The enrichment scores of 29 functional gene expression signatures in osteosarcoma samples were calculated by single sample gene set enrichment analysis (ssGSEA). TME classification of osteosarcoma was performed and a prognostic assessment tool was created based on 29 ssGSEA scores to comprehensively correlate them with TME components, immunotherapy efficacy and prognosis of osteosarcoma. RESULTS: Three TME subtypes were generated that differed in survival, TME activity and immunotherapeutic response. Four differentially expressed genes between TME subtypes were involved in the development of prognostic assessment tools. The established prognosis assessment tool had strong performance in both training and verification cohorts, could be effectively applied to the survival prediction of samples of different ages, genders and transfer states, and could well distinguish the TME status of different samples. CONCLUSIONS: The present study describes three different TME phenotypes in osteosarcoma, provides a risk stratification tool for osteosarcoma prognosis and TME status assessment, and provides additional information for clinical decision-making of immunotherapy.

When molecular outsmarts morphology: Malignant ossifying fibromyxoid tumors masquerading as osteosarcomas, including a novel CREBZF::PHF1 fusion.

We present two cases of malignant ossifying fibromyxoid tumor (OFMT) which eluded diagnosis due to compelling clinicopathologic mimicry, compounded by similarly elusive underlying molecular drivers. The first is of a clavicle mass in a 69 year-old female, which histologically showed an infiltrative nested and trabeculated proliferation of monomorphic cells giving rise to scattered spicules of immature woven bone. Excepting SATB2 positivity, the lesion showed an inconclusive immunoprofile which along with negative PHF1 FISH led to an initial diagnosis of high-grade osteosarcoma. Next generation sequencing (NGS) revealed a particularly rare CREBBP::BCORL1 fusion. The second illustrates the peculiar presentation of a dural-based mass in a 52 year-old female who presented with neurologic dyscrasias. Sections showed a sheeted monotonous proliferation of ovoid to spindle cells, but in contrast to Case #1, the tumor contained an exuberance of reticular osteoid and woven bone deposition mimicking malignant osteogenic differentiation. NGS showed a novel CREBZF::PHF1 fusion. Both tumors recurred locally less than 1 year post-operatively. As such we reiterate that careful morphologic examination is axiomatic to any diagnosis in our discipline, but this paradigm must shift to recognize that molecular diagnostics can provide closure where traditional tools have notable limitations.

High-grade osteosarcoma arising in DCIA flap reconstruction after a prior resection of maxillar cemento-ossifying fibroma: A case report.

Cemento-ossifying fibroma is a rare benign odontogenic tumour of the tooth-bearing jaws. Its concomitant occurrence with osteosarcoma, a malignant maxillofacial bone tumour, has never been described before. We present an uncommon case of a 43-year-old woman in whom a cemento-ossifying fibroma in the right maxilla was treated by resection and reconstruction using a deep circumflex iliac artery flap. During surgical prosthetic rehabilitation one-year post-operative, an osteosarcoma extending from the contralateral maxilla was coincidentally discovered in the deep circumflex iliac artery flap. The aim of this case report is to raise awareness on the extremely rare but possible simultaneous and independent occurrence of a cemento-ossifying fibroma and an osteosarcoma.

Single-cell aggrephagy-related patterns facilitate tumor microenvironment intercellular communication, influencing osteosarcoma progression and prognosis.

Osteosarcoma, a common malignant tumor in children, has emerged as a major threat to the life and health of pediatric patients. Presently, there are certain limitations in the diagnosis and treatment methods for this disease, resulting in inferior therapeutic outcomes. Therefore, it is of great importance to study its pathogenesis and explore innovative approaches to diagnosis and treatment. In this study, a non-negative matrix decomposition method was employed to conduct a comprehensive investigation and analysis of aggregated autophagy-related genes within 331,394 single-cell samples of osteosarcoma. Through this study, we have elucidated the intricate communication patterns among various cells within the tumor microenvironment. Based on the classification of aggregated autophagy-related genes, we are not only able to more accurately predict patients' prognosis but also offer robust guidance for treatment strategies. The findings of this study hold promise for breakthroughs in the diagnosis and treatment of osteosarcoma, intervention of aggrephagy is expected to improve the survival rate and quality of life of osteosarcoma patients.

Updates in Osteosarcoma.

Clinical care of osteosarcoma (OSA) in dogs has seen little change during the past 2 decades, relying on amputation and platinum-based chemotherapy for pain control and survival. Recent advancements offer hope for improved outcomes. Genomic research reveals shared genetic abnormalities between canine and human OSA. Multidimensional imaging provides valuable staging and prognostic information. Limb-sparing approaches including stereotactic body radiation therapy are routine. Ablative therapies such as microwave ablation and histotripsy show promise. Immunotherapy including cell therapy and immune checkpoint inhibition are available. Radiopharmaceuticals are tuned to target OSA cells directly. These innovations may enhance treatment and prognosis for dogs with OSA.

Diagnostic challenges in low-grade central osteosarcoma.

Aims: Low-grade central osteosarcoma (LGCOS), a rare type of osteosarcoma, often has misleading radiological and pathological features that overlap with those of other bone tumours, thereby complicating diagnosis and treatment. We aimed to analyze the clinical, radiological, and pathological features of patients with LGCOS, with a focus on diagnosis, treatment, and outcomes. Methods: We retrospectively analyzed the medical records of 49 patients with LGCOS (Broder's grade 1 to 2) treated between January 1985 and December 2017 in a single institute. We examined the presence of malignant features on imaging (periosteal reaction, cortical destruction, soft-tissue invasion), the diagnostic accuracy of biopsy, surgical treatment, and oncological outcome. Results: Based on imaging, 35 of 49 patients (71.4%) exhibited malignant features. Overall, 40 of 49 patients (81.6%) had undergone a biopsy before en-bloc resection: 27 of 40 patients (67.5%) were diagnosed on the first biopsy, which was more accurate when carried out by open rather than needle biopsy (91.3% vs 35.3% diagnostic accuracy, respectively; p < 0.001). Of the 40 patients treated by en-bloc resection, surgical margins were wide in 38 (95.0%) and marginal in two (5.0%). Furthermore, nine of 49 patients (18.4%) underwent curettage (intralesional margin) without previous biopsy. All patients with a positive margin developed local recurrence. Distant metastases occurred in five of 49 patients (10.2%). The mean five-year overall survival (OS) and distant relapse-free survival (D-RFS) were 89.3% (SD 5.1%) and 85.7% (SD 5.5%), respectively. Univariate analysis showed that the occurrence of distant metastasis was a poor prognostic factor for OS (hazard ratio 11.54, 95% confidence interval (CI) 1.92 to 69.17; p < 0.001). Local recurrence was a poor prognostic factor for D-RFS (HR 8.72, 95% CI 1.69 to 45.0; p = 0.002). Conclusion: The diagnosis of LGCOS can be challenging because it may present with non-malignant features and has a low diagnostic accuracy on biopsy. If precisely diagnosed, LGCOS can be successfully treated by surgical excision with wide margins.

Delay in Diagnosis and Treatment of Primary Bone Tumors.

BACKGROUND: Delay in the diagnosis and treatment of bone tumors continues to be a common problem. Prolonged diagnosis can significantly reduce the chances of successful treatment of the disease. Accordingly, the aim of this study was to assess the delay in the diagnosis of primary bone tumors, identify the most common symptoms and analyze the course of the diagnostic and therapeutic path. MATERIAL AND METHODS: Thirty-two (K=18; M=14) patients treated surgically for primary bone tumors were included in the retrospective study. Patient records were analyzed. Delay in diagnosis was defined as the time from the onset of symptoms to the initial diagnosis and referral to an orthopedic oncology center. RESULTS: The median delay in diagnosis was 7 (3-12) months. For tumors located in the pelvis, the delay was 10 months, compared to 5 months for the upper limb and 7 months for the lower limb (p=0.2312). The delay was 6 months In patients with osteosarcoma, and 8 months in chondrosarcoma patients (p=0.1786). At the first office visit, an x-ray was ordered in 19 cases (59.4%), of whom 9 patients (47.4%) were referred on to the oncology center. The most common symptoms were pain in the affected area (90.6%), limited mobility (28.1%) and pathological fracture (25%). After admission to an orthopedic department, a biopsy was performed after 5.5 (3-8.2) days. The histology results were ready after another 14 (8-18) days, and surgical treatment was performed after 95 (76-100) days. CONCLUSIONS: 1. Although patients show typical symptoms of bone tumors, only a small proportion are referred directly to an oncology center. After a primary bone tumor is suspected, further diagnostic and therapeutic activities proceed efficiently, in accordance with the current guidelines.

Telangiectatic osteosarcoma of maxilla in a young child.

Telangiectatic osteosarcoma (TO) is an uncommon variant of osteosarcoma that primarily afflicts young adults. In this case report, we describe a unique instance of TO occurring in a young child's maxilla. Under microscopic examination, it reveals abundant blood-filled spaces, extensive hemorrhagic regions, alongside atypical pleomorphic tumor cells and osteoid. It is crucial to conduct a meticulous histopathological examination to distinguish TO from other lesions, such as aneurysmal bone cysts and Ewing sarcoma.

The fibrinogen-albumin ratio as a novel prognostic factor for elderly patients with osteosarcoma.

To analyze the prognostic value of fibrinogen-albumin ratio (FAR) in predicting the overall survival in elderly osteosarcoma patients. One hundred nineteen elderly osteosarcoma patients (> 40 years old) from 2 centers were retrospectively reviewed and analyzed. The cutoff values of the biomarker were calculated via receiver operating characteristic curves, and the cohort was divided into high FAR group and low FAR group. The association between the FAR and clinical-pathological parameters was analyzed. And the prognosis of elderly osteosarcoma patients and the potential risk factors were analyzed using Kaplan-Meier method and Cox proportional hazards model. Finally, a clinical nomogram was constructed, and its predictive capacity was verified. According to receiver operating characteristic results, the cutoff value for FAR was 0.098, and the enrolled patients were divided into the low FAR group and high FAR group. The FAR was significantly correlated with several clinical-pathological characteristics, including age, tumor size, tumor stage, recurrence, and metastasis. Moreover, the multivariate Cox analyses results showed that the FAR, pathological fracture, and metastasis were independent risk factors for overall survival in elderly osteosarcoma patients. The predictive nomogram was subsequently constructed, representing satisfactory predictive performance for prognosis in elderly patients with osteosarcoma. The FAR value is a promising indicator for elderly osteosarcoma patients, which is correlated with the various clinical characteristics and prognosis. A clinical nomogram integrating FAR and other clinical indicators is a convenient and available tool to assess the prognosis and manage the individualized and precise treatment of elderly patients with osteosarcoma.

Cytokines as Prognostic Biomarkers in Osteosarcoma Patients: A Systematic Review and Meta-analysis.

Osteosarcoma is the most prevalent type of primary bone malignancy in children and adolescents. The effect of cytokines on osteosarcoma prognosis has been studied and reported. This meta-analysis aimed to assess the prognostic value of cytokines as osteosarcoma biomarkers. Databases including PubMed, Embase, and Cochrane Library were searched for studies on the prognostic value of cytokines in osteosarcoma. From the eligible studies, data on overall survival (OS), disease-free survival, and metastasis-free survival (MFS) were extracted. Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated. A total of 11 studies involving 755 patients were included in this analysis. High macrophage migration inhibitory factor (MIF) expression in tumors was significantly associated with shortened OS (HR = 2.01, 95% CI: 1.18-3.42, P = 0.010) and MFS (HR = 2.51, 95% CI: 1.47-4.01, P = 0.001). Elevated T cell immunoglobulin and mucin domain-3 (Tim-3) levels in serum correlated with increased risk of disease progression in patients with osteosarcoma (HR = 3.14, 95% CI: 2.88-3.03, P < 0.001). However, interleukin 6 (IL-6) and tumor necrosis factor were not substantially associated with osteosarcoma prognosis. Owing to a paucity of research, other relevant cytokines [interferon-α/ß receptor, tissue factor, macrophage inhibitory cytokine 1 (MIC-1), and IL-23] could not be combined. In conclusion, MIF levels in tumors and Tim-3 levels in serum can be potential biomarkers of poor prognosis in osteosarcoma. To confirm this finding and implement these biomarkers into clinical applications, additional large-scale, high-quality studies are needed.

Assessment of the Interval to Diagnosis in Pediatric Bone Sarcoma.

OBJECTIVES: The timely diagnosis of primary bone malignancies in pediatric patients is critical to clinical outcomes. The purpose of this study is to investigate the initial presentation of pediatric bone sarcoma patients to an academic health care system and assess the current interval to diagnosis. METHODS: We conducted a retrospective review of pediatric patients (aged 1-18) with biopsy-proven diagnosis of osteosarcoma or Ewing sarcoma presenting between 2004 and 2020. All living patients had 1 year or more of follow-up. Primary outcomes were interval to diagnosis, clinical features on initial presentation, percent of patients with negative radiographic workup at initial presentation, and number of health care encounters before diagnosis. RESULTS: Seventy-one patients (osteosarcoma, 51; Ewing sarcoma, 20) were included. Average age at presentation was 13.1 ± 3.3 years (range, 4.4-18.3). Average symptom duration was 5.4 ± 13.9 months (range, 0.1-84). Clinical features at initial presentation included limb/back pain (91.5% of patients), activity modification/pain medication use (78.9%), palpable mass (40.8%), night pain (35.2%), limp (25.4%), limb disuse (18.3%), and recent fever history (2.8%). Fourteen of 71 patients (19.7%) had negative radiographs at initial presentation. Average number of health care encounters before diagnosis was 1.9 ± 0.6 (range, 1.0-4.0), with most in the outpatient pediatrician clinics (81.2%) and emergency department (18.3%). Average time to diagnosis from initial presentation was 19.5 ± 65 days (range, 0-493); the 14 patients with initial negative radiographs had a statistically significant prolonged interval to diagnosis of 54 ± 134 days (range, 0-493; P = 0.018). CONCLUSIONS: We found pediatric patients with primary bone sarcoma present with an average interval to diagnosis of 20 days. Twenty percent of patients had a significantly prolonged interval to diagnosis of 54 days. Clinical features suggest night pain is not a sensitive indicator. In patients of appropriate age with persistent unilateral pain in suspicious locations, early advanced imaging with magnetic resonance imaging should be considered.