Neurotrophic tropomyosin receptor kinase (NTRK) gene fusions have emerged as important oncogenic drivers across a wide range of malignancies, including soft tissue sarcomas. Early detection of these fusions facilitates precision treatment with TRK inhibitors, significantly improving clinical outcomes. However, diagnosing NTRK-rearranged spindle cell neoplasms (NTRK-RSCNs) remains challenging due to their histological heterogeneity and overlap with other soft tissue tumors. We present the case of an 8-year-old boy with a history of infantile fibromatosis, who developed progressive right ankle dorsiflexion weakness and right foot drop. Magnetic resonance imaging revealed a large, homogeneously enhancing soft tissue mass with extensive perineural involvement and spinal cord compression spread from T8 to L3 levels. The patient underwent T10-L1 laminectomy and partial tumor resection under intraoperative neurophysiological monitoring. Histopathological analysis identified a low-grade spindle cell neoplasm with focal positivity for S100 and CD34, and patchy pan-tropomyosin receptor kinase (TRK) expression. Molecular studies using fluorescence in situ hybridization and RNA-based next-generation sequencing confirmed a TPM3-NTRK1 fusion, establishing the diagnosis of NTRK-rearranged low-grade spindle cell sarcoma. Postoperatively, targeted therapy with a TRK inhibitor Larotrectinib (100mg/m2/dose twice daily) was initiated. Over a 2-year follow-up period, the patient demonstrated significant neurological improvement and stable disease without evidence of progression on serial imaging studies. This case underscores the importance of integrating molecular diagnostics into the evaluation of atypical spindle cell tumors, particularly those presenting with aggressive clinical features despite low-grade histology. Early identification of NTRK fusions enables timely initiation of TRK inhibitor therapy, offering durable disease control and functional recovery. Broader awareness and implementation of molecular testing can greatly enhance the management of rare pediatric sarcomas.

BACKGROUND Solitary plasmacytoma of bone (SPB) is a rare malignant plasma cell neoplasm, comprising 6% of all plasma cell tumors. It is characterized by a solitary osteolytic lesion. CASE REPORT This report describes an asymptomatic SPB in the rib of a 66-year-old man. X-ray and computed tomography (CT) initially showed localized bone resorption and destruction of the right fifth posterior rib, with a 4.0×2.4×2.8 cm soft-tissue mass. Single-photon emission computed tomography (SPECT) confirmed isolated rib involvement without multifocal skeletal lesions. Pathology and immunohistochemistry (CD138+, CD38+) confirmed the SPB diagnosis. SPB usually presents as a single osteolytic lesion, which often occurs in the vertebrae and skull. Rib involvement in SPB is uncommon, due to its nonspecific imaging features, often causing diagnostic delays or misdiagnosis. Radiotherapy is the primary treatment for localized SPB. However, there is a 30% to 50% risk of progression to multiple myeloma (MM), necessitating long-term surveillance of serum M protein and periodic imaging. CONCLUSIONS This case emphasizes that for adult patients with isolated rib destruction with or without the formation of soft-tissue masses, the possibility of SPB should not be ruled out, even in the absence of typical clinical symptoms and clear imaging and laboratory examination evidence. Multimodal imaging and immunohistochemical analysis are critical for accurate diagnosis. Early intervention and regular monitoring optimize outcomes and reduce misdiagnosis risks. Regular follow-up is vital to detect disease changes early and adjust treatment plans promptly.

Beyond the third lumbar vertebra (L3): Thoracic computed tomography-derived muscle mass and quality assessment as a practical alternative for body composition analysis.

Acquired digital fibrokeratoma (ADFK) is a rare benign tumour that can be difficult to diagnose when unusually large or atypical in presentation. We report a man in his 50s with a slowly enlarging lesion on the fifth toe that reached 30mm over 2 years. MRI revealed a well-circumscribed soft tissue mass with homogeneous, low-signal intensity internally on T1- and T2-weighted images, without features of malignancy. Excisional biopsy confirmed ADFK, and the postoperative defect was reconstructed with a reverse digitolateral flap. After a year, there was no recurrence and both functional and cosmetic outcomes were favourable. This case represents an exceptionally rare presentation of giant ADFK and highlights the importance of preoperative imaging for accurate diagnosis and systematic treatment planning. Level of Evidence: Level V (Therapeutic).

Background: Adenoid cystic carcinoma (ACC) is a rare malignant tumor of the salivary glands, most frequently arising from the minor salivary glands of the palate. Despite its slow growth, ACC is characterized by an insidious course, marked perineural invasion, and a high propensity for local recurrence and distant metastasis. Early diagnosis remains challenging, as palatal lesions may initially mimic benign or inflammatory conditions. Case Presentation: We report the case of a female patient presenting with a painless palatal swelling initially misdiagnosed as a palatal abscess. Imaging revealed a soft-tissue mass with focal bone lysis and extension toward the maxillary sinus and nasal floor. Histopathological analysis confirmed ACC with predominant cribriform and tubular patterns and focal perineural invasion. The patient underwent radical surgical resection with oncologic margins, followed by reconstruction using a para-lateronasal approach and temporalis fascia flap. Discussion: This case illustrates the deceptive clinical presentation of palatal ACC and highlights the importance of advanced imaging in detecting subtle bone and sinus involvement. The histopathological features identified— particularly the cribriform/tubular architecture and perineural invasion—correlate with the known biological behavior of ACC. Radical surgery with postoperative radiotherapy remains the standard of care for resectable lesions, while long-term surveillance is critical due to the high rate of late recurrence and distant metastasis. Conclusion: Any persistent palatal swelling under intact mucosa should prompt consideration of ACC, especially when imaging demonstrates bone erosion or sinus extension. Early recognition, appropriate surgical planning, and vigilant follow-up are essential to optimize outcomes given the tumor’s aggressive and unpredictable behavior.

Retained surgical items pose a significant risk to patient's safety, with an estimated occurrence of 1 in 5500 procedures. Gossypibomas, also referred to as retained surgical sponges, are items unintentionally left in the cavities of the body after surgery. These adverse events can lead to secondary surgical procedures, readmissions, and infections. A 24-year-old Somalian male patient presented with persistent coughing, black sputum, and halitosis. His medical history included a laparotomy for a 5-year-old stab wound and penile amputation following a missile injury 15years back. Physical examination revealed pale conjunctiva, pallor in the oral mucosa, and spoon-shaped fingernails. A chest X-ray demonstrated a ball-like consolidation in the lower left chest, and a thoracic computed tomography scan revealed a soft tissue lesion. The patient underwent thoracotomy and laparotomy, along with a left lower lobe lobectomy due to a bronchopleural fistula caused by a large abdominal surgical sponge invading the lung parenchyma, forming a cavitary lung mass. Diaphragmatic defect was repaired and resection of the gastric perforation using a stapler was performed. The patient's postoperative course was uneventful. Gossypibomas should be considered as a potential differential diagnosis in patients presenting with thoracoabdominal soft tissue masses and having a history of prior surgery. This is especially relevant in cases involving gynecological or emergency surgeries, female sex, or individuals with a high body mass index. A detailed medical history and appropriate imaging are essential for timely diagnosis.

The aim of this case report is to describe comprehensive imaging such as CT scanning, endoscopy, histopathology, and clinical outcomes following medical and endoscopic treatment. A 5-year-old spayed female Chihuahua presented with chronic unilateral nasal discharge, congestion, and intermittent stertor, unresponsive to initial antibiotics and steroids. Further diagnostics, including endoscopy, revealed a cystic lesion with osseous fragments in the left nasal cavity, while CT imaging identified a soft tissue mass with associated bone resorption. Histopathology confirmed chondro-osseous respiratory epithelial adenomatoid hamartoma (COREAH), a rare benign lesion characterized by respiratory epithelium, fibrovascular proliferation, and osseous components, along with lymphoplasmacytic and eosinophilic inflammation. Clinical signs improved following endoscopic aspiration and drainage, which restored nasal cavity space. This case highlights the importance of combining endoscopy, advanced imaging, and histopathology for accurate diagnosis and effective management of COREAH, a condition with potential for recurrence. The use of endoscopy enabled real-time visualization and precise tissue sampling, distinguishing this case from others relying solely on imaging. This report contributes to the limited veterinary literature on COREAH and underscores the need for long-term monitoring due to its uncertain pathogenesis and variable presentation.

Coronary stent infection is very rare but can be life-threatening and may present with nonspecific symptoms. Conventional imaging can miss subtle peri-stent pathology. ECG-gated FDG PET/CT provides an accurate assessment by fusing metabolic and anatomic information, enhancing detection and guiding timely management in suspected stent infection. We report the case of a 65-year-old woman, 1.5 years post-LAD stenting, who presented with complaints of recurrent fever. ECG-gated FDG PET/CT showed an ill-defined soft tissue mass around the stent extending to the inner pericardium with elevated metabolic activity and a nearby loculated hypodense pericardial collection, indicative of stent infection. The patient had successfully managed with surgical intervention for stent removal and debridement along with antibiotics.

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a systemic inflammatory disorder characterized by abundant infiltration of IgG4-positive lymphocytes and plasma cells with fibrosis in the involved organs. Periarterial lesions are relatively rare manifestations of IgG4-RD, and their clinical and imaging findings remain unclear. A 66-year-old man presented with persistent upper abdominal pain. Contrast-enhanced computed tomography (CECT) showed a gradually enhanced 47mm soft tissue mass lesion adjacent to the pancreatic uncinate and spreading around the superior mesenteric artery. Considering the imaging findings, pancreatic cancer could not be ruled out. We decided to perform an endoscopic ultrasound-guided fine-needle biopsy to confirm the histological diagnosis; however, we could not obtain a sufficient amount of tissue. Finally, the patient was diagnosed with IgG4-related periarteritis by performing a percutaneous biopsy of the lesion. The patient was treated with oral prednisolone (PSL) and approximately six months after PSL induction, CECT revealed marked shrinkage of the lesion. Although imaging findings are important for diagnosis, histopathological findings are essential for accurate clinical diagnosis. All possible means, including percutaneous targeted biopsy, should be attempted to acquire sufficient tissue to confirm the pathological diagnosis to enable appropriate treatment.

Geriatric experts have long debated the inclusion of appendicular lean soft tissue mass (ALSTM) in the diagnostic criteria for sarcopenia. This study examined whether a diagnostic model for sarcopenia that excludes appendicular lean soft tissue mass (ALSTM) is equivalent to one that includes ALSTM in discriminating health-related outcomes. Community-dwelling older adults from the Itabashi Longitudinal Study on Aging in Tokyo, Japan, were included. Based on the AWGS2019 criteria, we developed two diagnostic models: Model 1, including low handgrip strength/gait speed and low ALSTM assessed by bioelectrical impedance analysis, and Model 2, excluding low ALSTM. Health-related outcomes were self-reported falls and hospitalization in the past year. Differences in area under the receiver operating characteristic curve (AUC) and 95% confidence intervals (CI) between the two models were estimated using 1000 bootstrap samples. In total, 2432 participants (median age: 76 years; 53.2% men) without missing data were analyzed. Falls and hospitalization were reported by 17.8% and 15.3% of participants, respectively. The AUCs [95% CIs] of Models 1 and 2 were 0.61 [0.59, 0.64] and 0.61 [0.58, 0.64] for falls and 0.65 [0.62, 0.68] and 0.64 [0.61, 0.67] for hospitalization, respectively. The differences (Model 2-Model 1) in AUCs [95% CI] between the two models were -0.004 [-0.015, 0.006] for falls and -0.004 [-0.014, 0.004] for hospitalization, with the CIs within the pre-specified equivalence margin (±0.05). Diagnostic models excluding ALSTM demonstrated equivalent discrimination ability to those including ALSTM, raising questions about the necessity of ALSTM assessment for sarcopenia diagnosis.

Abstract Background Nodular fasciitis (NF) is tumor-like, non-neoplastic disease. Objective Bone erosion due to nodular fasciitis is extremely rare and may resemble a malignant neoplasm radiologically. The aim of the current work was to present a rare case of nodular fasciitis of the finger associated with bone erosion, emphasizing its radiological and pathological features that may mimic malignancy, and to contribute to the differential diagnosis of similar lesions. Case presentation A 38-year-old man presented with a gradually enlarging, non-tender mass on the dorsal side of the right hand, associated with mild discomfort and restricted movement. Physical exam revealed a 1.5 cm mass adjacent to the second metacarpal bone. The ultrasound showed a 20 × 14 mm hypoechoic nodular lesion between the second and third metacarpal bones, closely related to the distal second metacarpal. X-ray revealed a well-defined, radiolucent lesion in the distal metaphysis without periosteal reaction. Computed tomography (CT) confirmed a lytic bone lesion with soft tissue involvement, but no aggressive features were observed. Magnetic resonance imaging (MRI) showed a soft tissue mass with internal cystic areas, heterogeneous contrast enhancement, surrounding soft tissue involvement, and bone marrow edema. Excision was performed due to a broad differential diagnosis, including enchondroma protuberance and tenosynovial giant cell tumor. Histological analysis showed a well-circumscribed nodular lesion composed of spindle cells in a myxoid-collagenous matrix, consistent with nodular fasciitis. Conclusions Nodular fasciitis is a rare, benign, and rapidly growing soft tissue lesion that can mimic malignancy both clinically and radiologically, posing a diagnostic challenge. Although it typically arises in subcutaneous tissues of the upper extremities, its occurrence in the hand, particularly with bone involvement, is sporadic. Imaging findings are often nonspecific, with variable ultrasound, CT, and MRI features that may resemble aggressive or malignant lesions. This case highlights an unusual presentation of NF with bone invasion in the hand, emphasizing the importance of including NF in the differential diagnosis of benign-appearing but locally aggressive lesions. Marginal excision remains the treatment of choice, with low recurrence rates when complete resection is achieved.

Introduction: Emergency physicians can use point-of-care ultrasound (POCUS) to identify lymph nodes in certain clinical scenarios, and advanced users can determine significant information (such as concerns for malignancy or differentiating them from abscesses for incision and drainage) based on a large volume of literature and images associated with those pathologies. However, current literature does not contain a similar volume of images and cases of suppurative lymph nodes, or buboes, limiting the ability to make the diagnosis sonographically at the bedside. Case Report: We report on a man who presented to the emergency department (ED) with a worsening inguinal mass that changed size with positioning, as well as a 20-pound weight loss occurring over the course of a month. Point-of-care ultrasound of the mass was concerning for a necrotic suppurative lymph node, which was further evaluated with cross-sectional imaging. The patient was admitted for a biopsy to rule out malignancy. He was discharged with serologies for Bartonella henselae pending, which later returned positive. The patient was then switched to azithromycin with significant improvement of his symptoms. Conclusion: As POCUS becomes the modality of choice for rapid assessment of soft tissue masses in the ED, familiarity with less common variants of soft tissue infections such as buboes can help with medical decision-making, risk stratification, and further workup. This sonographic description of a bubo caused by a common zoonotic infection will enable clinicians to familiarize themselves with their appearance.

A 64-year-old man presented with severe anemia (hemoglobin 56g/L; RBC 2.60×1012/L) on a background of hypertension, diabetes, coronary heart disease, and cerebral thrombosis. Contrast-enhanced abdominal CT and initial endoscopy were unremarkable. Initial 99mTc-RBC SPECT/CT scintigraphy localized active bleeding to the descending colon. However, repeat endoscopy revealed brown stool in the terminal ileum. Subsequent 99mTc-RBC SPECT/CT scintigraphy identified a small-bowel soft-tissue mass whose position shifted confirmed epithelioid angiosarcoma of the small intestine. This case highlights the utility of 99mTc-RBC SPECT/CT in diagnosing challenging small intestinal angiosarcoma.

BACKGROUND Paravertebral extraskeletal Ewing sarcoma located in the extradural region is uncommon. Muscle denervation can be caused by nerve injury, destruction of the neuromuscular junctions, and aging-related loss of motor neurons. Psoas denervation caused by spinal extraskeletal Ewing sarcoma is extremely rare. CASE REPORT A 38-year-old Chinese man presented to our hospital with back pain lasting for 1 month. He presented thoracolumbar mobility limitations. Magnetic resonance imaging revealed a well-defined margin extradural soft tissue mass involving the intervertebral foramen and paravertebral region at level L1-L2. The mass measured approximately 31×47×42 mm and demonstrated heterogeneous signal intensity on T1-weighted imaging and hyperintensity on STIR images. Imaging showed psoas compression, with diffuse homogeneous edema. On post-contrast images, the mass showed heterogeneous enhancement, and the edematous psoas showed homogeneous enhancement. Pathological examination of the biopsy specimen revealed clusters of atypical small blue round cells with hyperchromatic nuclei, scant cytoplasm, and frequent mitotic figures. Immunohistochemical analysis of tumor cells demonstrated strong membranous positivity for CD99 and nuclear positivity for NKX2.2. The final diagnosis was extraskeletal Ewing sarcoma. Chest computed tomography revealed multiple nodal metastases. The patient underwent chemotherapy for 4 cycles, and the tumor showed no response to treatment. The patient refused further chemotherapy and took only oral analgesic. He died 12 months after presenting to our hospital. CONCLUSIONS Extraskeletal Ewing sarcoma is a rare subtype in the Ewing sarcoma family of tumors. Spinal extradural extraskeletal Ewing sarcoma is uncommon, and masses compressing the lumbar plexus and causing psoas denervation is extremely rare.

This article reported on a case of unicentric chest wall Castleman disease, diagnosed by surgical pathology, which manifested primarily as oral mucosal erosions and bronchiolitis obliterans. The patient, a 25-year-old male, was admitted to the hospital on December 18, 2023, with an 11-month history of oral mucosal erosions and an 8-month history of dyspnea with reduced exercise tolerance. Pulmonary function tests revealed extremely severe obstructive ventilatory dysfunction with a negative bronchodilator response. Chest computed tomography (CT) scan showed a soft-tissue mass in the deep muscle layer of the left chest wall with enhancement. PET/CT demonstrated slightly increased metabolic activity at this site, with a maximum standardized uptake value (SUVmax) of 2.1. Additionally, the patient tested positive for BP-180 pemphigoid antibody. Taken together, the constellation of these findings could be explained by a unifying diagnosis, with histopathological confirmation being key. Surgical pathology of the chest wall mass confirmed the diagnosis of Castleman disease (hyaline vascular type). Ultimately, the patient was diagnosed with unicentric chest wall Castleman disease-associated paraneoplastic autoimmune multiorgan syndrome and successfully underwent bilateral lung transplantation approximately one year after diagnosis.

Introduction: Rosai-Dorfman disease (RDD) is a rare non-Langerhans cell histiocytosis with no well-established treatment approaches. Surgery is typically indicated for symptomatic patients, but adjuvant treatment to reduce recurrence is infrequently addressed in the literature. Case Presentation: Herein, we describe the case of a 77-year-old woman with a neurological deficit and an infiltrative epidural soft tissue mass at the T3 to T9 levels, as revealed by magnetic resonance imaging (MRI). Following complete tumor resection, pathological examination confirmed spinal RDD. The patient subsequently received postoperative radiotherapy with a dose of 30 Gy in 15 fractions four weeks later. At the eighteen-month postoperative follow-up, the patient was clinically improved and her MRI at one year showed no recurrence. Conclusions: Postoperative radiotherapy in spinal RDD remains controversial due to insufficient clinical evidence. Nevertheless, few case reports did not show treatment-related complications.

The likely first question to ask when encountering a soft tissue tumor for the first time is simply, "Is this carcinoma or sarcoma?" Lesions of unknown etiology should also nearly always include melanoma as a differential diagnosis due to its greatly elusive nature, and this case report reinforces the importance of also keeping a lymphoproliferative process at the forefront of one's mind while considering the possible overlapping features with other entities. We present a 64-year-old man with a soft tissue mass of the supraspinatus that was perceived as an epithelioid angiosarcoma due to the largely epithelioid morphology and characteristic immunohistochemical profile. However, given the patient's pertinent hematologic history and an additional array of immunohistochemical stains, the neoplasm was regarded as a myeloid sarcoma. Much like melanomas, lymphomas can present in a number of different forms and fashions. Namely, myeloid sarcomas-a mass-forming neoplasm composed of myeloid blasts effacing the surrounding tissue architecture-can masquerade as a carcinoma or sarcoma not only morphologically, but also immunohistochemically. We consider the pitfalls experienced with this entity and further elaborate on the genetics discovered within this particularly challenging lesion.

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.

BACKGROUND DEGCAGS syndrome is an exceptionally rare genetic disorder caused by mutations in the ZNF699 gene. It presents with a broad spectrum of clinical features, including neurodevelopmental delays and dysfunction or anomalies affecting the gastrointestinal, cardiovascular, genitourinary, and skeletal systems. Although these features have been described in the literature, reports of airway complications remain exceedingly rare. This report describes the case of a 1-year-old infant with a confirmed diagnosis of DEGCAGS syndrome who presented with progressive stridor and respiratory distress. CASE REPORT A 1-year-old girl with DEGCAGS syndrome (confirmed by ZNF699 mutation via whole-exome sequencing) presented with progressive stridor, hoarseness, respiratory distress, and feeding difficulties since birth. Despite prior suspicion of congenital laryngomalacia, her symptoms persisted. Clinical evaluation revealed microcephaly, coarse facial features, oropharyngeal masses, and developmental delay. Computed tomography and magnetic resonance imaging identified a nasopharyngeal soft-tissue mass and vocal cord edema. Fiberoptic nasopharyngoscopy demonstrated bilateral vocal cord dysfunction and laryngomalacia. Surgical resection of nasopharyngeal and tongue-base masses with supraglottoplasty was performed. Histopathology confirmed hamartomas. Postoperatively, the patient required transient ICU support but achieved stable respiration and normal feeding by discharge. Follow-up at 2 months revealed no recurrence or functional deficits. CONCLUSIONS To the best of our knowledge, this is the first documented case of multiple laryngeal hamartomas in a patient with DEGCAGS syndrome. This case emphasizes the need for heightened clinical vigilance in recognizing rare complications in genetic disorders and underscores the importance of a multidisciplinary approach to diagnosis and management.

Omentin-1 (also known as intelectin-1) is a novel adipokine associated with metabolic diseases. However, its physiological role in body composition remains incompletely understood. Therefore, this study aimed to investigate the association between the circulating omentin-1 levels and whole-body and regional body composition parameters measured using dual-energy X-ray absorptiometry (DXA). A population-based cross-sectional survey was conducted among school-aged children in Hamamatsu, Japan. Serum adipokine levels were measured using enzyme-linked immunosorbent assay, and associations between omentin-1 levels and DXA-based parameters were evaluated by multiple regression analysis after adjusting for potential confounding factors. The final study included 392 participants (192 boys, 200 girls, 75.2% of the source population; mean age 11.2 ± 0.3years). Serum omentin-1 levels showed a significantly inverse association with nearly all DXA-based fat mass parameters. Inverse correlations were observed with fat-free soft tissue mass and serum leptin levels, whereas positive correlations were noted with adiponectin levels. The mean values for various body fat parameters, fat-free soft tissue mass, body mass index, and waist circumference were significantly decreased across tertiles of serum omentin-1 levels from lowest to the highest after adjusting for potential confounders. Our results demonstrate that Japanese school-aged children with higher fat mass tended to have lower serum omentin-1 levels. These findings provide crucial insights into the link between omentin-1 levels and body composition, which may contribute to early health interventions for metabolic improvement.