Malignant aneurysmal bone cyst is not a well described concept. We present a case of a morphologically malignant bone tumour, interpreted as a malignant aneurysmal bone cyst with areas of characteristic morphology, a myofibroblastic phenotype, and a proven PAFAH1B1:USP6 fusion. The radiologic, morphologic and molecular features of this unusual case are discussed, along with the spectrum of atypical/malignant USP6 translocated tumours.

Open surgery is commonly used for treating benign bone tumours and tumour-like lesions near the joints of the extremities. However, inappropriate resection margins may lead to incomplete lesion removal and subsequent local recurrence, while overly extensive dissection aggravates soft tissue injury and compromises periarticular joint function. Although uniportal endoscopic technique have been well established in minimally invasive spinal surgery, their utilization in juxta-articular benign bone lesions remains poorly defined with unclear patient selection criteria and medium-term oncological performance. This retrospective study aimed to summarize the appropriate indications for uniportal endoscopic technique in the treatment of benign bone tumours and tumour-like lesions adjacent to limb joints and evaluate its oncological safety and local control outcomes. By comparing the differences between the uniportal endoscopic technique and open surgery in treating benign bone tumours and tumour-like lesions adjacent to limb joints, this study aims to investigate the feasibility of the uniportal endoscopic technique. More importantly, it aims to evaluate and discuss the indications of uniportal endoscopic technique, as well as the medium-term oncological efficacy and safety. A retrospective analysis was conducted on the clinical data of patients with benign bone tumours and tumour-like lesions near the joints of the extremities treated at the Affiliated Cancer Hospital of Chongqing University between October 2021 and December 2024. Among them, 53 patients were treated using the uniportal endoscopic technique, and 97 patients were treated using the open surgery. The follow-up period for all cases exceeded 12months. All cases had a definitive pathological diagnosis preoperatively. The lesion size (maximum diameter) was recorded for indication stratification. Primary study endpoints focused on medium-term oncological outcomes, including local recurrence rate and lesion clearance status evaluated by serial follow-up computed tomography (CT). Secondary perioperative indicators including operation time, intraoperative blood loss, postoperative complications, and preoperative and postoperative Visual Analogue Scale (VAS) scores were collected for comparison. Surgical outcomes were evaluated using the modified Macnab criteria. All 150 patients included in this study completed the follow-up examinations. During follow-up, adequate radical lesion clearance was confirmed on serial CT examinations in all patients, and no local recurrence was detected in both the uniportal endoscopic technique group and the open surgery group. All lesions enrolled in this study had a maximum diameter less than 5cm, and uniportal endoscopic technique achieved complete resection in these eligible cases, suggesting that a maximal diameter < 5cm represents a reasonable size indication for this endoscopic technique. Postoperative imaging examinations indicated satisfactory bone healing in all patients. The mean operation time was 140.02 ± 39.67min in the uniportal endoscopic technique group and 141.56 ± 36.90min in the open surgery group, with no statistically significant difference between the two groups (P > 0.05). Intraoperative blood loss was significantly lower in the uniportal endoscopic technique group compared with the open surgery group [20.00 (15.00) mL vs. 50.00 (50.00) mL; P < 0.001]. No postoperative complications occurred in either group. Intra-group comparison: The VAS scores at various postoperative time points were significantly lower compared to the preoperative scores in both groups (P < 0.05), indicating statistically significant improvement postoperatively. The results of the modified Macnab criteria at the final follow-up indicated significant improvement in clinical symptoms for all patients, suggesting postoperative pain relief, functional recovery, and improved quality of life. In conclusion, for juxta-articular benign bone tumours and tumour-like lesions with a maximum diameter less than 5cm, uniportal endoscopic technique achieves equivalent radical resection efficacy compared with open surgery under strict indication screening. No local recurrence was observed in either group during follow-up, which suggests the favourable oncological safety of the uniportal endoscopic technique. Although the uniportal endoscopic technique had advantages in several perioperative indicators, these minimally invasive benefits should not serve as the primary basis for surgical decision-making.

Indication-specific use of Denosumab in Giant Cell Tumour of Bone: A retrospective cohort study.

Allograft imaging in orthopaedic oncology - A tertiary sarcoma centre experience allograft imaging.

Evaluation of standardized uptake value (SUV) and apparent diffusion coefficient (ADC) as prognostic imaging parameters for primary Ewing sarcoma in hybrid 18F-FDG-PET/MRI.

Osteosarcoma is the most common primary bone tumour in dogs, with approximately 75% of cases occurring in the appendicular skeleton. Standard-of-care therapy consists of limb amputation followed by carboplatin chemotherapy. A minority of dogs have limb-sparing treatments including stereotactic body radiation therapy (SBRT) or surgery. SBRT has a high incidence of pathologic fracture (41%-80% of cases) following treatment, which often results in amputation or euthanasia. Prophylactic bone stabilisation following SBRT has not been recommended due to high complication rates. The IlluminOss system (IS) is an intramedullary implant consisting of a light-curable polymer within an inflatable balloon catheter, which is approved in humans for traumatic fractures and prevention of fractures secondary to bone metastases. We performed a study to assess the safety and feasibility of using the IS following SBRT in six dogs with suspected appendicular osteosarcoma. The IS was placed the day after completion of SBRT. Five of six dogs received adjuvant carboplatin chemotherapy. The IS was well tolerated with no implant-associated infections or immediate post-operative complications occurring. Pathologic fractures occurred in four dogs with a median fracture-free interval of 107 days. Three dogs ultimately underwent amputation due to pathologic fractures. No other post-operative complications occurred. The median survival time was 156 days. These findings suggest that the IS may be a palliative option for dogs following SBRT, but further research to optimise use in the dog and evaluation of the use of the IS with ancillary fixation is necessary.

Osteoblastoma is a rare primary bone tumour, and the lesions are typically intracortical affecting long-bone metaphysis and the posterior spine. The histological hallmark is characteristic networks of trabeculated woven bone, usually lined by osteoblasts within a vascularised stroma. This case report details an unusual case of an intramedullary osteoblastoma of the femur. A 22-year-old male presented with an eight-month history of right knee pain on a background of a previous distal tibia non-ossifying fibroma. The patient underwent cross-sectional imaging, and a biopsy was obtained confirming a lesion in the distal femoral diametaphysis. MRI showed multiple internal fluid levels and septations with a sclerotic rim and associated marrow oedema, cortical sclerosis, and periosteal soft tissue oedema. Subsequent biopsy provided histological confirmation of osteoblastoma. This case is presented to highlight the rare anatomical location for osteoblastoma: in the medullary canal of the distal femur.

The aim of this study was to achieve consensus on important topics related to tenosynovial giant cell tumour (TGCT) and giant cell tumour of bone (GCTB), and to identify areas for future research. In January 2026, a consensus meeting, The Birmingham Orthopaedic Oncology Meeting (BOOM), held in Cape Town, South Africa, gathered 314 delegates from 59 countries to debate 21 consensus statements on tenosynovial giant cell tumour (TGCT) and giant cell tumour of bone (GCTB) through a modified Delphi process. Of the 21 statements, two achieved unanimous consensus, 18 strong consensus, and one moderate consensus. Unanimous consensus was reached for prioritizing joint-preserving intralesional curettage in GCTB when feasible, and for supporting non-surgical approaches in anatomically challenging cases, particularly sacral lesions. The statement addressing the role of denosumab in GCTB achieved only moderate consensus. The use of adjuvants in GCTB, as well as the management of recurrent and systemic GCTB, including long-term use of denosumab, reached strong consensus. Strong consensus was achieved in the surgical and non-surgical management for both primary and recurrent TGCT. Surveillance strategies for both TGCT and GCTB generated substantial discussion despite strong consensus, reflecting ongoing uncertainty and lack in evidence. This international consensus provides practical guidance for the management of TGCT and GCTB while identifying important gaps in evidence. Joint-preserving surgery remains central to the treatment of GCTB, with selective integration of systemic therapies and individualized surveillance. The consensus framework highlights priorities for future collaborative research in orthopaedic oncology.

Optimisation of osteosarcoma sample processing for epigenetic analysis: A comparative evaluation of formalin-fixed, paraffin-embedded samples with and without decalcification versus fresh tissue.

Age-related real-world treatment patterns and outcomes of localised, high-grade osteosarcoma.

Combined endoprosthetic replacement of the ipsilateral distal femur and proximal tibia is rarely performed. It is usually undertaken to achieve limb salvage after resection of primary bone tumours around the knee. This study aims to determine the viability of 'composite' endoprosthetic reconstruction around the knee, and report implant survival and limb salvage rates. A retrospective review of a prospectively maintained departmental database was undertaken to identify patients who had undergone composite endoprosthetic reconstruction around the knee. The primary outcome of interest was revision-free implant survival. Secondary outcomes were amputation-free survival, the Musculoskeletal Tumor Society (MSTS) score, and extensor lag. A total of 34 patients (21 male and 13 female) with a mean age of 32 years (14 to 66) underwent surgery between January 1997 and November 2024, and were followed up for a median interval of 12.6 years (IQR 3 to 14). The oncological diagnoses were osteosarcoma (n = 26), Ewing's sarcoma (n = 5), and one each of giant cell tumour of bone, spindle cell sarcoma, chondrosarcoma, and synovial sarcoma. Of the eight primary and 26 revision cases, the pooled five- and ten-year revision-free implant survival rates were 77% (95% CI 63 to 94%) and 61% (95% CI 45 to 83), respectively (Kaplan-Meier). Resection length and construct:stem ratio had no impact on revision rate. Limb salvage at five and ten years was 81% (95% CI 68 to 96) and 69% (95% CI 54 to 89), respectively. Range of motion outcomes were available in 30 patients and MSTS scores in 20 patients. The mean extensor lag was 25° (10° to 50°) and the mean MSTS score was 53% (27% to 67%). Composite endoprosthetic reconstruction around the knee after tumour resection is a viable limb salvage option in the primary or revision setting; however, it does carry a risk of reoperation in the medium and long term. The leading reason for failed limb salvage in the long term is infection. We recommend careful patient selection and preoperative discussion before contemplating composite reconstruction.

Role of chest imaging in GCTB staging and surveillance.

Chondrosarcomas are tumours that typically occur in older adults. Although afew arise denovo, they often develop from pre-existing enchondromas, much more frequently from osteochondromas. In these secondary chondrosarcomas, the primary site of pre-existing chondrogenic lesion plays an important role (close to the trunk, centrally; appendicular skeleton, peripherally). Thus, low-grade chondrosarcomas in the periphery are referred to as atypical chondrogenic tumours (ACT), whereas tumours of the same histopathological type located close to the axial skeleton are called chondrosarcoma grade1. Syndromal occurrence (Ollier's and Maffucci's diseases) carries asignificantly higher risk of malignant transformation. Other malignant primary bone tumours being much less frequent exhibit an unspecific osteolytic morphology but sometimes at atypical location (chordoma: sacrococcygeal region; adamantinoma: tibial shaft; malignant giant-cell tumor [GCT]: epi-metaphyseal expansion). Subsequent histological evaluation frequently reveals the (unexpected) diagnosis. For this reason, one section will focus on tumour mimics and differentiation from benign bone lesions. In this respect, some associated aspects of the well-known Lodwick (Madewell) classifications are discussed in order to highlight three very peculiar bone tumour-associated imaging phenomena (periosteal reactions, aneurysmatic bone cyst-like changes, peritumoral reactive zones).

From bone alterations to tumours: Genetic drivers linking Paget's disease of bone to cancer.

Skeletal metastasis of unknown primary at the initial visit represents a clinically important subset of metastatic bone tumours, accounting for ~7.8%-21.7% of all skeletal metastases. This condition differs from cancer of unknown primary (CUP), in which the primary site remains unidentified after comprehensive evaluation. At this diagnostic entry point, before completion of a full work-up, early stratification is essential; however, the clinical utility of serum tumour markers at this stage remains unclear. We retrospectively reviewed 79 patients who presented with skeletal metastasis of unknown primary at the initial visit before diagnostic work-up between January 2010 and October 2023. Clinical characteristics, final primary diagnoses, types of tumour markers measured, positivity rates, and diagnostic performance were analysed. Haematologic malignancies were the most frequent final diagnoses (40.5%), followed by lung (22.8%) and prostate cancer (10.1%). A total of 17 tumour markers were measured (mean, 6.3 per patient; range, 0-12). Prostate-specific antigen (PSA), immunoelectrophoresis (IEP), soluble interleukin-2 receptor (sIL-2R), and thyroglobulin (Tg) showed high sensitivity and specificity for prostate cancer, multiple myeloma, malignant lymphoma, and thyroid cancer, respectively. Carcinoembryonic antigen (CEA) and cytokeratin 19 (CK19, CYFRA 21-1), although not organ-specific, were frequently positive in carcinomas and served as indicators of epithelial malignancy. Serum tumour markers can assist early diagnostic stratification at the initial presentation of skeletal metastasis before primary-site identification. A selective testing strategy focusing on sIL-2R, IEP, CEA, and CK19, with PSA added in men and Tg when clinically indicated, may improve diagnostic efficiency and provide a basis for considering a bone-metastasis-oriented diagnostic approach.

BackgroundOsteosarcoma (OS) is the most common primary malignant bone tumour in adolescents, and pulmonary metastasis remains the leading cause of death. In skeletally immature patients, the avascular physis is considered a barrier to local tumour spread, but its relationship to lung metastasis has not been quantified.MethodsWe conducted a single-centre, retrospective cohort study of 32 paediatric OS patients. Tumour–physis relationships were evaluated before and after chemotherapy using standard local staging and chest CT. The primary outcome was pulmonary metastasis at last follow-up, analysed with multivariable logistic regression including age, sex, tumour size, location, laterality, and physeal breach. A complementary orthotopic tibial xenograft model was established by injecting 143B cells into nude mice, creating physeal-breach and non-breach groups. Vascular endothelial growth factor (VEGF) immunohistochemistry (IHC) assessed angiogenic activity at the tumour–physis interface.ResultsPulmonary metastases were present in 22% at diagnosis and in 50% (16/32) by last follow-up. Physeal breach was the only independent predictor of metastasis (odds ratio 59.89; 95% CI 3.34–1073.95; p=0.006). In the xenograft model, pulmonary metastases developed in all physeal-breach mice and in none of the non-breach group. VEGF IHC showed increased angiogenic activity in breach-associated tumours.ConclusionPhyseal breach identifies a biologically aggressive subset of paediatric OS with high metastatic potential. Because breach status is readily appreciable on routine imaging, it may serve as a practical biomarker to refine risk stratification, predict pulmonary metastasis and guide evaluation of anti-angiogenic strategies.

Background/Objectives: Osteosarcoma is the most common primary malignant bone tumour, affecting children and young adults. Recent evidence suggests that extracellular vesicles (EVs), small membrane-bound nanoparticles released by all cell types, play a key role in intercellular communication within the tumour microenvironment. Therefore, we aimed to investigate the effects of osteoblast-derived EVs (OB-EVs) on osteosarcoma cell behaviour and to characterise the transcriptional and miRNA-mediated mechanisms underlying these effects. Methods: Phenotypic assays were performed to assess metabolic activity, proliferation, apoptosis, and invasion ability of human osteosarcoma cell lines after treatment with OB-EVs. Illumina-based RNAseq was conducted on RNA isolated from OB-EVs-treated cells, and qRT-PCR was assessed using commercially available TaqMan miRNA cards on RNA isolated from OB-EVs. Results: In U2OS cells, OB-EVs reduced metabolic activity (1.30-fold decrease, p = 0.0137) and proliferation (1.70-fold decrease, p = 0.017) while increasing apoptosis (1.15-fold increase, p = 0.014). In MG63, OB-EVs increased proliferation (4.9-fold increase, p = 0.020) without affecting tumour cell aggressiveness, while normal osteoblast behaviour was not affected by OB-EVs. MNNG/HOS cells treated with OB-EVs for 48 h showed substantial transcriptomic changes, with 296 differentially expressed genes (97 up- and 199 down-regulated in OB-EVs treated cells versus untreated cells), indicating a direct impact of OB-EVs on gene expression. Intriguingly, Gene Set Enrichment Analysis (GSEA) showed trends consistent with modulation of signalling pathways, including Wnt/β-catenin and NOTCH. Conversely, miRNA profiling of OB-EVs identified 13 highly expressed miRNA. Integration of transcriptomic and miRNA target prediction data highlighted convergent pathway-level signals, suggesting that OB-EVs may modulate tumour-associated regulatory networks. Conclusions: Taken together, these findings indicate that OB-EVs modulate osteosarcoma cell phenotype, with miRNA shuttling representing a potentially relevant contributing mechanism. The integrative analysis suggests that pathways associated with proliferation and cellular homeostasis, including Wnt/β-catenin signalling, may be involved, although further functional validation is required to confirm these mechanisms.

Bone tumours constitute a heterogeneous group of lesions with overlapping clinical and radiological features, making accurate preoperative diagnosis challenging. Correlating clinical findings and imaging with histopathology may improve diagnostic confidence and guide management. The present study aimed to evaluate the clinical and radiological profile of bone tumours and to determine the degree of clinico-radiological concordance with histopathology, which served as the gold standard. This hospital-based pilot observational study included 34 patients with suspected bone tumours who underwent clinico-radiological evaluation followed by histopathological confirmation. Demographic and clinical details were obtained from case records. Radiological assessment was based on plain radiography and MRI, with additional CT and PET-CT as indicated. Lesions were assessed for age predilection, anatomical site, bone segment involved, pattern of destruction, margin, cortical breach, periosteal reaction, matrix mineralisation, and soft-tissue extension. A provisional clinico-radiological diagnosis was assigned in each case. Histopathological diagnosis served as the gold standard. Data were analysed using descriptive statistics and diagnostic performance indices. The mean age at presentation was 24.14 ± 13.17 years, with the highest incidence in the 10-19-year age group (44.1%). Males accounted for 73.5% of cases. Long bones were affected in 88.2% of cases, the most common being the femur (41.2%). Histopathology revealed malignant tumours in 73.5%, benign tumours in 20.6%, and non-neoplastic or inflammatory lesions in 5.9%. The most frequent final diagnosis was osteosarcoma (47.1%), followed by giant cell tumour (17.6%) and Ewing sarcoma (14.7%). Family-level clinico-radiological concordance was 47.1%, rising to 70.6% when the final diagnosis was included among radiological differentials. The sensitivity, specificity, and overall diagnostic accuracy for detecting malignancy were 84.0%, 77.8%, and 82.4%, respectively. Clinico-radiological evaluation is valuable for preliminary diagnosis, biological stratification, and narrowing the differential diagnosis of bone tumours; however, histopathology remains indispensable for definitive diagnosis and accurate tumour classification.

This study evaluated the accuracy of resection of bone tumours and the fit between host bone and massive bone allograft (MBA) in children with malignant bone tumours of lower limb who underwent surgery using in-house 3-dimensional (3D)-printed patient-specific instruments (PSIs)for tumour resection and graft-specific instruments (GSIs)for shaping the MBA. This retrospective study included sevenchildren (3 males, 4 females; median age 13) with malignant bone tumours of the lower limb who underwent intercalary resection and reconstruction with MBA between September 2023 and March 2025 using in-house designed 3D-printed PSIs and GSIs. Tumours were located in the femur(5 children) and tibia(2 children). We analysed the accuracy of bone resection, complications of reconstruction, and function of patients. All resections achieved R0 margins. The median planned resection length was 16.5cm versus 16.8cmactually resected(median difference 0.2cm). Bone union was achieved in 13 of 14 (92.9%) osteotomy sites. Bone union was faster at metaphyseal junctions (median 5.9months) than diaphyseal junctions (median 8.4months) (p = 0.01). One of the osteotomy sites (7.1%) had a delayed union requiring secondary bone grafting. The median Musculoskeletal Tumour Society score was 30 at the last follow-up. 3D-printed PSIs and GSIsappear to enhancethe accuracy of bone tumour resection and host bone-MBA fit,thereby reducingthe risks of inadequate margins and non-union, respectively.

Bizarre parosteal osteochondromatous proliferation (BPOP), or Nora's lesion, is a rare benign bone tumour that most commonly affects the bones of the hands and feet. It presents diagnostic challenges due to its aggressive imaging features, high recurrence rate and histological overlap with malignant lesions. We report the case of an adolescent girl who presented with a hard, ulcerated swelling over the distal phalanx of the right great toe. Imaging revealed corticomedullary continuity of the lesion with the underlying phalanx, raising suspicion for osteochondroma or subungual exostosis. Surgical excision was performed, and histopathology confirmed BPOP, showing binucleated chondrocytes, endochondral ossification and the characteristic 'blue bone'. No recurrence was observed during a 1-year follow-up period. This case highlights the importance of considering BPOP in the differential diagnosis of toe lesions particularly when atypical radiological features are present. Histopathological examination remains the cornerstone for definitive diagnosis.