Marrow pyroptosis ignites the periosteal reaction.

A man in his seventies with an incidentally detected scapular osteochondroma showed progressively increasing FDG uptake on serial 18 F-FDG PET/CT, while the CT component initially revealed no definite signs of malignant transformation. On the final PET/CT, however, CT images showed a periosteal reaction suggestive of extracortical extension, raising strong concern for malignancy. Biopsy was followed by tumor resection, and postoperative pathology confirmed secondary peripheral chondrosarcoma (grade 3). The patient later developed widespread metastases. This case underscores that increased or rising FDG uptake in an osteochondroma may indicate early malignant transformation, emphasizing careful assessment even when CT changes are minimal.

Osteoarthritis (OA) is a common degenerative joint disease in the elderly. It is characterized by articular cartilage degradation and periosteal bone spur formation. These changes often lead to pain, tissue compression, and disability. Periosteum-derived progenitor cells (PDPCs) play a crucial role in periosteal reactions, relying on vascular endothelial cells (VECs) for signal transduction through vascular networks. While bone-related studies often emphasize tissue regeneration, the intercellular signaling mechanisms driving OA progression remain underexplored. This study developed a vascularized bone-on-paper platform to simulate a three-dimensional (3D) periosteum-vascular tissue microenvironment. The platform consisted of a paper substrate sandwiched between a PDPCs/hydrogel construct and a Matrigel layer seeded with VECs. This configuration enabled coculture under inflammatory conditions to mimic the periosteum-vascular interface. The platform facilitated the investigation of cellular crosstalk and vascular development during bone degeneration. Results revealed that this platform effectively analyzed key signaling factors, including IFN-γ, TNF-α, IL-1β, IL-6, IL-10, IL-8, and VEGFA, at different stages of bone inflammation. Neutralizing and vascular development assays further demonstrated the significant role of these factors in the aberrant proliferation of PDPCs and vascular development. This platform provides a novel approach for studying intercellular signaling in bone degenerative progression and offers valuable insights for developing targeted therapies. By linking extracellular symptoms with signaling mechanisms, it advances understanding of OA pathogenesis and therapeutic innovation.

Proliferative Periostitis: Often Overlooked Onion-Skinning.

Extrapulmonary tuberculosis (TB) contributes significantly to the disease burden in Southeast Asia, yet maxillofacial involvement is rare and often misdiagnosed due to nonspecific features such as swelling, ulceration, or trismus. Conventional microbiology shows low sensitivity in these paucibacillary lesions, emphasizing the role of rapid molecular tests such as Cartridge-Based Nucleic Acid Amplification Testing (CBNAAT). This case series outlines the diagnostic challenges of maxillofacial TB in an endemic region. Nine patients (aged 9-33 years) presented with chronic lesions in maxillofacial region. Imaging commonly demonstrated osteolysis, cortical breach, periosteal reaction, or soft-tissue abscess. Mantoux testing, cytology, and Ziehl-Neelsen staining were often inconclusive, whereas CBNAAT or culture confirmed Mycobacterium tuberculosis in most cases. All patients received standard anti-tubercular therapy with significant clinical and radiographic improvement. Maxillofacial TB should be considered in persistent jaw lesions. Early molecular testing enhances diagnosis and supports timely, effective therapy.

To evaluate imaging features and clinicopathologic correlation in florid reactive periostitis (FP) and parosteal osteosarcoma (PO), emphasizing diagnostic pitfalls in surface bone lesions. Four patients (two FP, two PO) underwent radiography, CT, and MRI, including dynamic contrast-enhanced sequences in selected cases. Histopathology with immunohistochemical analysis of MDM2 and CDK4, including gene amplification testing, was performed in all cases. FP demonstrated solid or layered periosteal reaction, soft-tissue swelling, and bone marrow edema without atypia or MDM2/CDK4 amplification. PO presented as lobulated ossified masses with cortical attachment or cleavage plane and positive MDM2/CDK4 expression. DCE-MRI showed overlapping enhancement patterns and did not reliably differentiate the entities. Differentiation between FP and PO requires careful evaluation of conventional imaging features combined with histopathological confirmation. Multidisciplinary assessment remains essential to prevent diagnostic overtreatment or undertreatment. · FP may mimic PO on MRI. · Cleavage plane favors parosteal osteosarcoma. · DCE-MRI shows overlapping enhancement patterns. · MDM2/CDK4 are essential in equivocal cases. · Igrec J, Stranger N, Puseljic M et al. Imaging Pitfalls in Surface Bone Lesions: Florid Reactive Periostitis Mimicking Parosteal Osteosarcoma - A Multimodality Case Series. Rofo 2026; DOI 10.1055/a-2864-1949.

Benign metastasizing leiomyoma is a rare entity characterized by the metastasis of histologically benign smooth muscle tumors that originate from uterine leiomyomas. Patients are typically women with a history of uterine leiomyomas for which they have undergone operative treatment. Benign metastasizing leiomyoma most frequently involves the lungs but has been described in other locations. Osseous involvement is rare, with less than 20 cases reported in literature, the majority occurring in the spine. The current case is that of a 67-year-old female with a history of breast carcinoma with multiple lytic osseous lesions involving the pelvis and scapula, initially suspected to represent metastatic disease. Following multi-modality imaging workup including radiographs, CT, MRI, and PET/CT, biopsy revealed benign metastasizing leiomyoma. This case illustrates the multimodality imaging appearance of this rare entity. Radiographs and CT typically show well-defined lytic lesion(s) without aggressive periosteal reaction. On MRI, lesions are often T1 and T2 hypointense, with diffuse enhancement following the administration of contrast. Lesions typically display no or mild FDG uptake on PET/CT, however, varying levels of FDG uptake have been reported in literature. Benign metastasizing leiomyoma with osseous involvement is a rare but clinically significant entity that requires a high index of suspicion in women with a history of uterine leiomyomas and new bone lesions. Radiologists should be aware of this entity so that they may include benign metastasizing leiomyoma in the differential diagnosis when appropriate.

To characterize peri-implant-medication-related osteonecrosis of the jaw (PI-MRONJ) (epidemiological, clinical, and radiographic features) in order to optimise its diagnosis and management. This is a retrospective cohort study including patients diagnosed with MRONJ that developed spontaneously around previously osseointegrated and loaded dental implants. Data were extracted from medical records. Outcome parameters included the underlying health condition, onset time, age, distinct radiographic features using 3D imaging, severe complications and systemic comorbidities. Patients were categorised into oncologic or osteoporotic groups. Forty patients (86 implants) were diagnosed with PI-MRONJ between 2015 and 2024. The mean age was 72.1. Radiographic features distinct from peri-implantitis included-osteolysis (80%), the most prevalent radiographic feature, osteosclerosis (57.1%), sequestration (54.3%), periosteal reaction and inferior alveolar canal involvement (30.8% each) and maxillary sinus involvement (77.8% of maxillary cases). A delay in diagnosis (only two cases [5%] were diagnosed at stage 1) was confirmed. Consequently, severe complication rates were high (38.7% for mandible and 55.6% for maxilla). Patients had an average of 3.1 systemic comorbidities. Oncologic patients showed a shorter onset time from antiresorptive treatment to diagnosis (mean 2.8 vs. 6.2 years, p < 0.001). PI-MRONJ may clinically and radiographically resemble peri-implantitis. However, it appears to represent a distinct and underrecognised subtype of MRONJ. Consequently, a delay in diagnosis occurs (stage 3). The advanced diagnostic stage aggravates a high rate of severe complications. A diagnostic flowchart is proposed to aid in differential diagnosis. Advanced age (> 70 years) and distinct radiographic features are suggested as hallmark features.

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).

Evidence of bony stress syndrome in a fossil cetacean.

Palmar cortical ridges on hand CT: Normal but misleading cortical adaptations and a potential diagnostic pitfall.

The range of possible inflammatory changes in the oral cavity and in the maxillary and mandibular bones may present with diverse patterns and characteristics in both clinical and radiological evaluation. In most cases, a standard radiological examination, such as dental panoramic radiograph (DPR), has significant limitations in assessing early or complex bone changes associated with chronic bone inflammation. Advanced imaging with multidetector computed tomography or cone-beam computed tomography (MDCT or CBCT) can improve lesion characterization and surgical planning when a detailed evaluation of tooth-bearing structures, tooth apices, cortical plates, and cancellous bone is required. Such imaging allows more detailed assessment of alterations in medullary bone morphology and architecture, as well as identification of possible periosteal reactions adjacent to chronic bone inflammation. Osteomyelitis of the jaws comprises a heterogeneous group of inflammatory bone disorders characterized by variable clinical presentations and a broad spectrum of radiological appearances. Depending on disease chronicity, host factors, and microbial burden, mandibular osteomyelitis may mimic odontogenic tumors, fibro-osseous lesions, or malignant bone pathologies. Quite often, dental treatment affects bone status and condition, leading to unwanted events such as bone inflammation. Imaging plays a central role in diagnosis; however, radiographic findings are often nonspecific, particularly in early or chronic stages. Each case of osteomyelitis underscores the importance of correlating imaging findings with clinical history and highlights the role of repeated imaging in distinguishing inflammatory bone disease from aggressive jaw lesions. This study aims to characterize diverse patterns of chronic mandibular osteomyelitis associated with various prior treatment modalities using CBCT. By presenting a series of illustrative cases from heterogeneous clinical settings, the authors highlight the nonspecific radiographic features and diagnostic challenges inherent in chronic bone inflammation. The focus remains on the interpretation of complex imaging findings rather than a comparative analysis of technical protocols.

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.

Odontogenic myxoma (OM) is a benign tumor originating from odontogenic ectomesenchyme. While this tumor displays imaging variability, the sunburst appearance is uncommon and can resemble malignant lesions. In this report, we present two cases of OM exhibiting an imaging sunburst appearance, besides a literature review. A 35-year-old woman and a 21-year-old woman presented with mandibular swelling. Imaging exams revealed extensive radiolucent/hypodense images, with the presence of a sunburst periosteal reaction. The main diagnostic hypothesis for both cases was osteosarcoma. Incisional biopsies were performed, with definitive diagnosis of OM. The first patient underwent simple surgical excision, while the second underwent en bloc resection. Neither patient experienced recurrence during the follow-up period of three and one year after treatment. Odontogenic myxoma should be considered in the differential diagnosis of jaw lesions presenting a sunburst periosteal reaction, as this atypical imaging pattern may mimic aggressive or malignant conditions.

ObjectiveEn-bloc excision with limb salvage is the gold standard for aggressive bone tumors around the knee, but up to 15% of cases occur in skeletally immature patients, creating a risk of limb-length discrepancy. Growing distal femoral prostheses with passive sliding tibial components address this issue but introduce unique mechanical challenges and potential complications. This study aimed to evaluate the incidence of tibial pain and complications beneath extendable distal femoral endoprostheses, and to correlate clinical symptoms and revision surgery.MethodsThe study comprised a retrospective review of 31 extendible distal femur endoprostheses from a single tertiary institution between 2008 and 2018. Measurements of radiographic parameters included coronal alignment, cortical thickness, cortical stem distances, stress shielding, and pedestal and periosteal reaction. The radiographic features were correlated with clinical evidence of tibial pain and the need for subsequent revision of the tibial component.Results17 patients reported tibial pain during the follow-up period, with a mean time of onset of 62.2 months (range, 27–132). There were 14 revisions in 12 patients, 4 revisions for tibial pain. Stress shielding and pedestal formation were seen in all patients after 28 months following insertion. Lateral cortical hypertrophy was more prominent in the group with pain with a mean thickness of 5.8 mm (range, 4–9.8). Varus shift of the tibial stem was radiographically evident during follow-up (n = 18). 95% of the patients with tibial pain had radiographic evidence of stem migration, 88% showed a periosteal reaction, and 76% had varus malalignment. In 13 patients (76%) with pain, all three of these parameters were present.ConclusionThere is a strong correlation between radiographic evidence of tibial stem migration and periosteal reaction and the development of symptoms. Patients should be warned of the need for revision of the tibial component for pain during the lifetime of the implant.Level of evidenceIV.

Primary malignant bone tumours are rare (about 0.2% of all malignancies) whereby-according to age-both osteosarcoma and Ewing's sarcoma are the most frequent bone sarcomas in children and adolescents. Both sarcomas are highly-malignant tumours with poor prognosis (Ewing's sarcoma) in particular when metastasized (osteosarcoma). There is abroad diagnostic armamentarium available, allowing precise detection of such tumours. However, alertness and familiarity of (early) radiological signs (such as periosteal reactions) are prerequisites to arouse suspicion. Radiological methods (plain radiography, magnetic resonance imaging [MRI], computed tomography [CT], ultrasonography) will be discussed regarding their pathomorphological clues. Likewise, both use and significance of more advanced imaging modalities (dual-energy CT, photon-counting CT; the Dixon technique and MRI with ultrashort time-to-echo [TE] sequences) are reviewed.

This study aimed to determine the diagnostic yield of CT-guided bone biopsies in pediatric patients, the outcome of non-diagnostic CT biopsy results, and to establish factors associated with non-diagnostic biopsy results. This is a retrospective study of consecutive pediatric patients ≤ 21 years who underwent CT-guided bone biopsies in three tertiary referral hospitals from December 2011 to March 2022. Clinical information, pre-biopsy CT and MRI images, procedural details, pathological results, and follow-up were assessed. Fisher's exact test was used to compare categorical variables. Mann-Whitney U-test and unpaired t-test were used to compare non-parametric and parametric variables, respectively. Statistical significance was set a p < 0.05. A total of 138 patients (mean age 13.9 ± 4.5 years; 95 (60%) male patients) with 157 CT-guided bone biopsies were studied, which yielded 38.2% (60/157) non-diagnostic, 23.6% (37/157) benign, and 38.2% (60/157) malignant results. Most non-diagnostic lesions (88.3% [53/60]) were subsequently determined to be benign. Factors associated with non-diagnostic biopsy results were cystic lesions (p = 0.003) incidental lesions (p = 0.03), fewer (p = 0.02) and shorter (p = 0.01) tissue cores, non-aggressive radiological features, including narrow zone of transition (p < 0.001), sclerotic margin (p < 0.001), no cortical destruction (p < 0.001), no periosteal reaction (p < 0.001), or no extra-osseous soft tissue mass (p < 0.001). About one-third of CT-guided bone biopsies in pediatric patients yielded non-diagnostic results, though most were ultimately confirmed to be benign. In children and adolescents with suspected primary bone tumors, CT-guided bone biopsy with non-diagnostic histopathological results strongly favors benignity in lesions with non-aggressive imaging features and should align management towards a more conservative approach. Question Limited data exist on the prevalence and outcome of non-diagnostic CT-guided bone biopsy in pediatric patients to guide clinical management. Findings About one-third of CT-guided bone biopsies in pediatric patients were non-diagnostic, though most were ultimately benign. Lesions with non-aggressive features were associated with non-diagnostic results. Clinical relevance In the setting of multidisciplinary care for patients with suspected primary bone tumors, non-diagnostic CT-guided bone biopsy-particularly in lesions with non-aggressive imaging features-strongly favors benignity, which should steer management towards a more conservative approach.

The growth plate is important in new bone developing; therefore, its injury may cause closing the plate in premature period and effect on growth of the bone. This injury can lead to deformity of the skeleton, if not treated correctly and not monitored for a long time. This study was aimed to evaluate radiographically the role of autogenous cartilage grafts impregnated with Magnesium Oxide Nanoparticles (MgONPs) in growth plate regeneration and in preventing the bone bridge formation at the growth plate defect. Ten adult rabbits were divided into two groups: a control group and an MgO group. A 2 mm section of the proximal tibia's growth plate was surgically removed from all rabbits. In the control group, the gap was filled with an autogenous ear cartilage graft soaked in normal saline. While in the MgO group, the gap was filled with an autogenous graft soaked in a 50 µg/ml MgONPs solution. Post-surgery, both groups showed immediate lameness. However, lameness resolved in the MgO group after 3 days in compared to the control. The radiographic results in 7, 14, 21, and 28 days after surgery showed early growth plate closure in the control group, without limb shortening or angular deformity. In contrast, the MgO group exhibited a small periosteal reaction around the growth plate gap, with no evidence of bone bridge formation. local application of MgONPs to a growth plate defect may postpone bone bridge formation, potentially preventing bone growth disorders. This finding highlights a promising strategy for managing growth plate injuries.

The World Health Organization introduced substantial revisions in the 2020 fifth edition of the classification system for bone and soft-tissue tumors, reorganizing what were previously called the Ewing sarcoma family of tumors or Ewing-like sarcomas into a new category of "undifferentiated small round cell sarcomas" based on molecular genetic characteristics. This reclassification established four distinct entities: Ewing sarcoma (ES), CIC-rearranged sarcoma, sarcoma with BCOR genetic alterations, and sarcoma with EWSR1-non-ETS fusion genes. Each subtype may demonstrate specific clinical, pathologic, and imaging features, with different treatment responses and prognoses. ES primarily affects children and young adults, with characteristic "moth-eaten" lytic bone destruction, aggressive periosteal reactions, and extensive surrounding soft-tissue masses. CIC-rearranged sarcomas typically manifest as well-circumscribed lobulated soft-tissue masses with extensive internal necrosis and hemorrhage but no calcification. Sarcomas with BCOR genetic alterations commonly occur in adolescent boys as osteolytic or sclerotic lesions in the long bones or the pelvis, often with calcification in the extraosseous component. Sarcomas with EWSR1-non-ETS fusion genes may manifest as osteolytic lesions with cortical expansion and saucer-like surface erosion in long bone diaphyses. Radiologic recognition of CIC-rearranged sarcomas enables oncologists to anticipate their aggressive nature and poor response to standard ES treatments, which may necessitate more intensive initial surgical interventions. In comparison, identifying BCOR-CCNB3 sarcomas through imaging allows clinicians to inform patients of their potentially more favorable outcomes compared with those of ES while still applying appropriate comprehensive treatment approaches. The authors provide an overview of the clinical features, pathologic findings, imaging characteristics, differential diagnosis, and treatment outcomes of each entity. ©RSNA, 2026.

Osteomyelitis (OM) is an infection of the bone that can present with a broad spectrum of clinical, laboratory, and radiological findings. Its diagnosis remains a clinical challenge, especially due to a range of non-infectious conditions that can mimic its presentation. These mimickers, both inflammatory and neoplastic, can lead to delayed or inappropriate management if not correctly identified. This review aims to highlight and analyze the key mimickers of OM, elucidate the distinguishing features of each, and provide a framework for clinicians to navigate these diagnostic challenges using an evidence-based, multidisciplinary approach. A comprehensive literature review was performed using different published articles in peer-reviewed journals. Emphasis was placed on recent advances in imaging modalities, including radiograph, computed tomography scan, magnetic resonance imaging, radionuclide scan, and their role in differentiating mimickers. Key mimickers of OM include bone tumors (e.g., Ewing sarcoma, lymphoma, osteoid osteoma), inflammatory arthropathies (e.g., gout, rheumatoid arthritis, chronic recurrent multifocal osteomyelitis [CRMO]), metabolic bone diseases (e.g., Charcot arthropathy), and post-traumatic bone changes. Imaging findings often overlap, such as marrow edema, periosteal reaction, or cortical destruction. However, certain features – like a nidus in osteoid osteoma or diffuse uptake patterns in metabolic bone disease, multifocal manifestation in CRMO can guide the diagnosis. Distinguishing OM from its mimickers is imperative for targeted management and optimal patient outcomes. Accurate diagnosis necessitates a holistic approach combining clinical history, laboratory investigations, advanced imaging, and, where necessary, biopsy. Greater awareness and understanding of these mimicking conditions among radiologists, pathologists, and clinicians can prevent misdiagnosis and facilitate timely intervention.