Pigmented Villonodular Synovitis Research Articles

Active surveillance of diffuse-type tenosynovial giant cell tumors: A retrospective, multicenter cohort study

BackgroundDiffuse-type tenosynovial giant cell tumor (D-TGCT) is a mono-articular, soft-tissue tumor. Although it can behave locally aggressively, D-TGCT is a non-malignant disease. This is the first study describing the natural course of D-TGCT and evaluating active surveillance as possible treatment strategy. MethodsThis retrospective, multicenter study included therapy naïve patients with D-TGCT from eight sarcoma centers worldwide between 2000 and 2019. Patients initially managed by active surveillance following their first consultation were eligible. Data regarding the radiological and clinical course and subsequent treatments were collected. ResultsSixty-one patients with primary D-TGCT were initially managed by active surveillance. Fifty-nine patients had an MRI performed around first consultation: D-TGCT was located intra-articular in most patients (n = 56; 95 %) and extra-articular in 14 cases (24 %). At baseline, osteoarthritis was observed in 13 patients (22 %) on MRI. Most of the patients’ reported symptoms: pain (n = 43; 70 %), swelling (n = 33; 54 %). Eight patients (13 %) were asymptomatic.Follow-up data were available for 58 patients; the median follow-up was 28 months. Twenty-one patients (36 %) had radiological progression after 21 months (median). Eight of 45 patients (18 %) without osteoarthritis at baseline developed osteoarthritis during follow-up. Thirty-seven patients (64 %) did not clinically deteriorate during follow-up. Finally, eighteen patients (31 %) required a subsequent treatment. ConclusionActive surveillance can be considered adequate for selected therapy naïve D-TGCT patients. Although follow-up data was limited, almost two-thirds of the patients remained progression-free, and 69 % did not need treatment during the follow-up period. However, one-fifth of patients developed secondary osteoarthritis. Prospective studies on active surveillance are warranted.

Does excision of giant cell tumor from the finger affect sensorineural innervation?

Giant Cell Tumor of the Tendon Sheath (GCTTS), often manifested as a nodular mass in the hand, presents significant challenges for surgical intervention, particularly when located in the fingers. This study aimed to evaluate the impact of GCTTS excision on sensory function and to explore the relationship between surgical outcomes and factors such as smoking and nerve dissection. A retrospective analysis was conducted on 28 patients diagnosed with GCTTS in the fingers, who underwent surgical excision between March 2017 and March 2023. Preoperative and postoperative sensory functions were assessed using two-point discrimination and Semmes-Weinstein monofilament tests. The results indicated no significant difference in sensory function 6 months post-surgery, suggesting that meticulous surgical technique can mitigate the risk of iatrogenic nerve damage. The study highlights the importance of comprehensive diagnostic methodologies, including thorough medical history, physical examination, and radiological imaging, in guiding surgical strategies. Moreover, it emphasizes the significance of meticulous preoperative planning and the potential for preserving sensory function following GCTTS excision.

Knee Tuberculosis Masquerading as Pigmented Villonodular Synovitis: A Challenging Diagnostic Case Report

Background: Tuberculous arthritis presents a diagnostic difficulty due to its modest clinical indications and vague imaging data, frequently resulting in a delayed or wrong diagnosis. Pigmented villonodular synovitis (PVNS), which might seem like tuberculous arthritis, complicates the diagnosis. Case Report: This case study features a young child whose knee arthritis was first misdiagnosed as PVNS. Magnetic resonance imaging (MRI) revealed nodular masses and hemosiderin deposits around the knee joint, indicating widespread PVNS. This error caused a delay in accurate diagnosis and treatment. Conclusion: These findings underscore the relevance of investigating TB in patients who appear with PVNS-like characteristics, emphasizing the necessity for a high index of suspicion and quick examination to achieve fast and correct diagnosis for successful care.

A High-Speed Ski Crash Leading to a Unique Synovial Cause for Knee Pain

The presented case involves the evaluation, diagnosis, and management of a 20-year-old male high-level skier who presented with persistent right knee pain following a ski crash. The patient reported hitting his right knee against a tree during the accident, resulting in intermittent swelling and a sensation of a mass within the knee. Despite some initial improvement in the sensation, the pain then became persistent and worsened by activity. Physical examination revealed limited symptoms during gait and functional movements, as well as restricted medial joint line tenderness and a mildly positive McMurray's test on the right knee. Magnetic resonance imaging findings prompted an orthopedic referral, leading to a right knee arthroscopy. The procedure involved resection of nodular synovitis and a diffuse synovectomy, with pathology confirming pigmented villonodular synovitis (PVNS). Despite post-operative complications, including methicillin-resistant Staphylococcus aureus bacteremia, ultimately, the patient's recovery was successful with the gradual restoration of pain-free range of motion through physical therapy. Follow-up assessments and magnetic resonance imaging scans indicated sustained improvement and no signs of pigmented villonodular synovitis recurrence.

Medium-term Outcomes of Excision Using Surgical Microscope of Tenosynovial Giant Cell Tumors of the Hand.

The recurrence rate following the excision of tenosynovial giant cell tumors (TSGCT) of the hand is very high. Intraoperative application of a surgical microscope has been reported. However, to date, there are no reports of medium-term outcomes related to this technique. This study aimed to evaluate the medium-term outcomes of tumor excision using surgical microscope for TSGCT of the hand. A total of 27 patients, who underwent an initial surgery for histologically-confirmed TSGCT of the hand, between 2008 and 2020, were included and evaluated. The mean follow-up time postoperatively was 6.8 years. Tumor recurrence and preoperative tumor characteristics were assessed. All tumors were adherent to tendons, tendon sheaths, neurovascular structures or periarticular ligaments and capsules. Bony lesions were observed in 11 tumors. The surgical microscope was used in 13 tumors. Recurrences were observed in three tumors (overall recurrence rate: 11%). Tumor characteristics were similar in both groups, but the recurrence rate in the group treated using the surgical microscope was 0%, whereas the recurrence rate in the group treated without the surgical microscope was 21%. Re-operations using the surgical microscope for recurrent tumors were performed, without recurrence postoperatively. Among patients with TSGCT of the hand treated with tumor excision using the surgical microscope, the postoperative recurrence rate was 0%. Based on the results of this study, the surgical microscope might be used for excision of TSGCTs of the hand.

What Are the Recurrence Rates, Complications, and Functional Outcomes After Multiportal Arthroscopic Synovectomy for Patients With Knee Diffuse-type Tenosynovial Giant-cell Tumors?

What Are the Recurrence Rates, Complications, and Functional Outcomes After Multiportal Arthroscopic Synovectomy for Patients With Knee Diffuse-type Tenosynovial Giant-cell Tumors?

Localized-Type Tenosynovial Giant Cell Tumors of the Upper Extremity: A 20-Year Retrospective Study with 139 Patients

Localized-Type Tenosynovial Giant Cell Tumors of the Upper Extremity: A 20-Year Retrospective Study with 139 Patients

MRI sequences at different degrees of flexion to investigate knee popping: an unusual way to diagnose an isolated pigmented villonodular synovitis lesion.

Knee popping is a frequent symptom among knee disorders which requires further investigation in case of a recent evolution of the symptom or pathological associated ones. This article reports a rare presentation of pigmented villonodular synovitis (PVNS), identified as the cause of knee popping symptoms, by performing MRI sequences at various degrees of knee flexion for a patient complaining from a gradual onset of knee popping, occurring when bending the knee over 120° of flexion. MRI sequences were performed just before the popping occurs (flexion 90°) and right after it had occurred (flexion 120°). The latter confirmed the origin of the symptom as the lesion moved forward, passing brutally through the interstice between the PCL and the ACL at 120° of flexion, explaining the popping. Treatment decision was to perform an arthroscopic resection of the lesion. Diagnosis of isolated PVNS was confirmed after anatomopathological analysis.

Diffuse Tenosynovial Giant Cell Tumor of the Wrist with Joint Destruction and Invasion

Abstract A 54-year-old man took antitubercular drugs for 1 year for right wrist pain, swelling, and restriction of movements, with no improvements. Magnetic resonance imaging wrist reported multiple nodules and soft-tissue mass with intraosseous erosions involving carpal bones, distal radius, and ulna. Resection of the mass, excision of the distal ulna, and wrist arthrodesis were done. The histopathology confirmed a diffuse tenosynovial giant cell tumor (TSGCT). No postoperative radiotherapy or systemic therapies were given. The patient remained symptom-free at 2 years of follow-up. Diffuse TSGCT with joint destruction and invasion of the wrist is rare. Therefore, a high index of suspicion is required before considering the most common infective etiologies in the wrist.

Overview of Pharmacological Therapies for Diffuse Tenosynovial Giant Cell Tumor

Tenosynovial giant cell tumor (TGCT) is a rare and locally aggressive benign tumor arising from the synovium of joints, bursae, and tendon sheaths. It is classified into localized (L-TGCT) and diffuse (D-TGCT) forms based on the extent of involvement. Surgical resection is the primary treatment, though achieving a definitive cure remains challenging due to the high recurrence rates, especially in D-TGCT. Systemic therapies targeting the CSF1-CSF1R axis have emerged as promising treatment options. CSF1R tyrosine kinase inhibitors (TKIs) such as imatinib, nilotinib, pexidartinib, and vimseltinib, alongside anti-CSF1R antibodies like emactuzumab, cabiralizumab, and lacnotuzumab, have shown encouraging results in managing TGCT, particularly when surgery is not feasible or poses significant morbidity. Other potential therapies, including local treatments and anti-inflammatory drugs, are being explored for TGCT management. This review provides an overview of systemic treatment options for D-TGCT, highlighting emerging therapeutic modalities and their potential implications. Effective management is crucial due to TGCT’s significant morbidity despite its non-life-threatening nature, necessitating novel approaches to improve patient prognosis and quality of life.

Abstract C160: HMPL-653, a highly potent and selective CSF-1R inhibitor, targeting both tumor cells and tumor microenvironment

Abstract Background: Colony stimulating factor 1 receptor (CSF-1R) and its ligand CSF-1 (CSF-1R/CSF-1) signaling regulates the function and survival of tumor-associated macrophages (TAM), which are involved in tumor progression and suppression of anti-tumor immunity. Moreover, activation of CSF-1R/CSF-1 axis including CSF-1 fusions or CSF-1R activating mutations has also been implicated in the pathogenesis of certain tumors such as tenosynovial giant cell tumor and histiocytic neoplasms. HMPL-653 is a highly potent and selective CSF-1R small molecule inhibitor, discovered and being currently developed in phase I clinical trial (NCT05277454) by HUTCHMED. Methods: The inhibition on CSF-1R kinase was determined using Z-LYTE™ kinase assay. The selectivity of HMPL-653 was assessed against a panel of 413 kinases by Eurofins. Cellular target inhibition on phosphorylation of CSF-1R (p-CSF-1R) was detected by ELISA. In vitro cell viability was measured by CCK-8 assay. Multiple CSF-1/CSF-1R driven tumor models in Nu/Nu nude mice were applied to determine the anti-tumor activity of HMPL-653 as a single agent. To demonstrate the immunoregulatory effect of HMPL-653, a murine tumor model, B16F10, was established in C57BL/6J mice, and the combination regimen, HMPL-653 plus PCP (poly (I:C)+CpG+anti-PD-1) was evaluated. Results: HMPL-653 strongly inhibited CSF-1R kinase with IC50 of 5 nM, showing >7-fold potency than that of the approved CSF-1R inhibitor pexidartinib (IC50=39 nM). And the selectivity profiling in 413 kinase panels revealed that HMPL-653 was highly potent only against CSF-1R, indicating a lower off-target risk than paxidatinib reported. HMPL-653 potently inhibited CSF-1 stimulated p-CSF-1R in THP-1 cells with IC50 of 5 nM. In CSF-1/CSF-1R-dependent cell lines, M-NFS-60 (mouse myelogenous leukemia) and three cell lines stably expressed BCR-CSF-1R or CSF-1R mutations (Ba/F3-BCR-CSF-1R, Ba/F3-CSF-1RW450-E456del, and Ba/F3-CSF-1RY546-K551del), HMPL-653 significantly down regulated p-CSF-1R and its downstream signaling p-ERK and p-AKT. As a consequence, HMPL-653 robustly inhibited the cell viability of above cell models (IC50s: 3~40 nM). Besides the direct anti-tumor effect, HMPL-653 also demonstrated strong inhibition on macrophage survival and M2 macrophage polarization, indicating a potential effect on targeting tumor microenvironment. In vivo, oral administration of HMPL-653 induced remarkable and dose-dependent anti-tumor efficacies in M-NFS-60 ascites model and subcutaneous tumor models harboring above mentioned CSF-1R alterations. And the PK/PD analysis revealed that the anti-tumor effect correlated well with p-CSF-1R inhibition. Moreover, HMPL-653 significantly improved the anti-tumor activity of PCP regimen in B16F10 model by reducing TAMs including M2 macrophages and increasing the ratio of M1/M2 macrophages. Conclusion: HMPL-653 is a highly potent and selective CSF-1R small molecule inhibitor which targets both CSF-1/CSF-1R-dependent tumors and tumor associated macrophages, warranting further clinical evaluation. Citation Format: Jia Hu, Liang Ge, Hui Zhang, An Jiang, Juntao Yu, Weifang Xue, Jian Wang, Yang Sai, Na Yang, Weiguo Qing, Yongxin Ren, Michael Shi, Weiguo Su. HMPL-653, a highly potent and selective CSF-1R inhibitor, targeting both tumor cells and tumor microenvironment [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C160.

Exploring the Effect of Compound Glycyrrhizin and Silybinin on the Metabolism of Pexidartinib in Rats Based on CYP3A4 and CYP2C9

Pexidartinib offered a new therapeutic option for adult patients with symptomatic tenosynovial giant cell tumor (TGCT) who were refractory to surgical treatment and had severe morbidity or functional limitations. Meanwhile, the metabolism of pexidartinib was mainly mediated through the oxidation of cytochrome P450 (CYP) 3A and glucuronidation by uridine glucuronosyltransferase (UGT) 1A4 and attention shall be paid to CYP450-based drug-drug interactions during therapeutic dosing. This study aimed to examine the changes in the pharmacokinetics of pexidartinib by silymarin and compound glycyrrhizin on pexidartinib in vivo in rats by high-performance liquid chromatography (HPLC)-UV approach and to detect its expression in CYP3A4 and CYP2C9 using the western blot. The findings of chromatography experiments revealed that silybinin as well as compound glycyrrhizin increased the exposure of pexidartinib in rats and had a significant inhibitory effect on the metabolism of pexidartinib. The results of immunoblotting assays suggested that silybinin as well as compound glycyrrhizin inhibited the protein expression of CYP3A4 and CYP2C9 in rats. Therefore, the combination of pexidartinib with silybinin and compound glycyrrhizin should be monitored to avoid clinical adverse effects.

Digitalized diagnosis and treatment of pigmented villonodular synovitis of temporomandibular joint: a case report.

Pigmented villonodular synovitis (PVNS) is a rare locally aggressive benign tumor in the temporomandibular joint (TMJ). This paper presents a patient with TMJ-PVNS involving masseteric space, temporal bone, zygomatic process, and mandibular ramus. Digital technique was used to determine the boundary of the lesion and reconstruct the normal glenoid fossa. The temporalis myofascial flap was transplanted between titanium mesh and condyle to reconstruct the disk after the complete resection of the tumor. The patient's facial profile is symmetrical, with a mouth ope-ning of 43 mm. No local recurrence and complications, such as cerebrospinal fluid fistula and encephaloceles, were detected during 30-month follow-up period.

Identification of potential diagnostic biomarkers for tenosynovial giant cell tumour by integrating microarray and single-cell RNA sequencing data

PurposeTenosynovial giant cell tumour (TGCT) is a benign hyperplastic and inflammatory disease of the joint synovium or tendon sheaths, which may be misdiagnosed due to its atypical symptoms and imaging features. We aimed to identify biomarkers with high sensitivity and specificity to aid in diagnosing TGCT.MethodsTwo scRNA-seq datasets (GSE210750 and GSE152805) and two microarray datasets (GSE3698 and GSE175626) were downloaded from the Gene Expression Omnibus (GEO) database. By integrating the scRNA-seq datasets, we discovered that the osteoclasts are abundant in TGCT in contrast to the control. The single-sample gene set enrichment analysis (ssGSEA) further validated this discovery. Differentially expressed genes (DEGs) of the GSE3698 dataset were screened and the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of DEGs were conducted. Osteoclast-specific up-regulated genes (OCSURGs) were identified by intersecting the osteoclast marker genes in the scRNA-seq and the up-regulated DEGs in the microarray and by the least absolute shrinkage and selection operator (LASSO) regression algorithm. The expression levels of OCSURGs were validated by an external dataset GSE175626. Then, single gene GSEA, protein–protein interaction (PPI) network, and gene-drug network of OCSURGs were performed.Result22 seurat clusters were acquired and annotated into 10 cell types based on the scRNA-seq data. TGCT had a larger population of osteoclasts compared to the control. A total of 159 osteoclast marker genes and 104 DEGs (including 61 up-regulated genes and 43 down-regulated genes) were screened from the scRNA-seq analysis and the microarray analysis. Three OCSURGs (MMP9, SPP1, and TYROBP) were finally identified. The AUC of the ROC curve in the training and testing datasets suggested a favourable diagnostic capability. The PPI network results illustrated the protein–protein interaction of each OCSURG. Drugs that potentially target the OCSURGs were predicted by the DGIdb database.ConclusionMMP9, SPP1, and TYROBP were identified as osteoclast-specific up-regulated genes of the tenosynovial giant cell tumour via bioinformatic analysis, which had a reasonable diagnostic efficiency and served as potential drug targets.

Computational exploration of the significance of COPS6 in cancer: Functional and clinical relevance across tumor types.

The COP9 signalosome subunit 6 (COPS6) has been implicated in cancer progression, while its precise role in most types of cancer remains elusive. To investigate the functional and clinical relevance of COPS6 across various tumor types using publicly available databases. We used R software and online analysis databases to analyze the differential expression, prognosis, mutation and related functions of COPS6 in pan-cancer. Differential expression analysis and survival analysis demonstrated that COPS6 was highly expressed and associated with high-risk profiles in the majority of cancer types. Possible associations between COPS6 expression level and prognostic outcomes were found using data from public databases. Mutational analysis revealed that missense mutations were the predominant type of COPS6 mutation. Additionally, positive correlations were identified between COPS6 expression level and tumor mutational burden and microsatellite instability in most types of cancer. Immune infiltration analysis demonstrated a negative correlation between COPS6 expression level and CD8+ T cell infiltration in certain types of cancer. The correlation between COPS6 expression level and cancer-associated fibroblast infiltration exhibited heterogeneity, in which a positive correlation was found in head and neck squamous cell carcinoma and tenosynovial giant cell tumor, and a negative correlation was identified in diffuse large B-cell lymphoma and thymoma. The correlation between COPS6 expression level and macrophage infiltration was closely related to macrophage type. Gene co-expression and enrichment analysis highlighted transcription elongation factor B polypeptide 2 and G protein pathway suppressor 1 were significantly and positively associated with COPS6 expression level. These genes were predominantly involved in processes, such as ubiquitin-mediated proteolysis and human immunodeficiency virus 1 infection. In conclusion, this study systematically explored the significance of COPS6 across different tumor types, providing a solid foundation for considering COPS6 as a novel biomarker in cancer research.

CSF1 expression in xanthogranulomatous epithelial tumor/keratin-positive giant cell-rich tumor

“Xanthogranulomatous epithelial tumor” (XGET) and “keratin-positive giant cell-rich soft tissue tumor” (KPGCT), two recently described mesenchymal neoplasms, likely represent different aspects of a single entity. Both tumors are composed of only a small minority of tumor cells surrounded by large numbers of non-neoplastic inflammatory cells and histiocytes, suggesting production of a paracrine factor with resulting “landscape effect,” as seen in tenosynovial giant cell tumor. Recent evidence suggests that the paracrine factor in XGET/KPGCT may be CSF1, as in tenosynovial giant cell tumor. We hypothesized that CSF1 is overexpressed in XGET/KPGCT. To test our hypothesis, we performed quantitative real time PCR (qPCR) for CSF1 expression and CSF1 RNAscope chromogenic in situ hybridization (CISH) on 6 cases of XGET/KPGCT. All cases were positive with CSF1 CISH and showed increased expression of CSF1 by qPCR. Our findings provide additional evidence that the CSF1/CSF1R pathway is involved in the pathogenesis of XGET/KPGCT. These findings suggest a possible role for CSF1R inhibition in the treatment of unresectable or metastatic XGET/KPGCT.

Synovial chondromatosis: Rare involvement of metacarpophalangeal joint and diagnostic challenges in MR imaging.

Synovial chondromatosis (SC) is a rare benign tumor of the cartilaginous tissue that frequently affects large joints intra-articularly. Characteristic imaging findings were reported for the diagnosis of SC. Herein, we report a case of SC of the metacarpophalangeal joint with atypical MRI findings. Considering the clinical presentation, erosion, absence of calcification on X-ray and CT, and low intensity on short tau inversion recovery (STIR), tenosynovial giant cell tumor was the initially diagnosis. However, histopathological findings revealed SC with fibrosis, which was confirmed using Elastica Van Gieson (EVG) staining. In general, low intensity on STIR in SC indicate calcification; however, it can also represent fibrosis in SC. In this case, the diagnosis of SC using MRI was limited highlighting the importance of histopathological findings for an accurate diagnosis of SC.

Tenosynovial giant cell tumours: experience at an Australian tertiary referral centre for musculoskeletal tumours with minimum two-year follow-up

AimsTenosynovial giant cell tumour (TGCT) is a rare benign tumour of the musculoskeletal system. Surgical management is fraught with challenges due to high recurrence rates. The aim of this study was to describe surgical treatment and evaluate surgical outcomes of TGCT at an Australian tertiary referral centre for musculoskeletal tumours and to identify factors affecting recurrence rates.MethodsA prospective database of all patients with TGCT surgically managed by two orthopaedic oncology surgeons was reviewed. All cases irrespective of previous treatment were included and patients without follow-up were excluded. Pertinent tumour characteristics and surgical outcomes were collected for analysis.ResultsThere were 111 total cases included in the study; 71 (64%) were female, the mean age was 36 years (SD 13.6), and the knee (n = 64; 57.7%) was the most commonly affected joint. In all, 60 patients (54.1%) had diffuse-type (D-TGCT) disease, and 94 patients (84.7%) presented therapy-naïve as "primary cases" (PC). The overall recurrence rate was 46.8% for TGCT. There was a statistically significant difference in recurrence rates between D-TGCT and localized disease (75.0% vs 13.7%, relative risk (RR) 3.40, 95% confidence interval (CI) 2.17 to 5.34; p < 0.001), and for those who were referred in the ”revision cases” (RC) group compared to the PC group (82.4% vs 48.9%, RR 1.68, 95% CI 1.24 to 2.28; p = 0.011). Age, sex, tumour volume, and mean duration of symptoms were not associated with recurrence (p > 0.05).ConclusionRecurrence rates remain high even at a tertiary referral hospital. Highest rates are seen in D-TGCT and “revision cases”. Due to the risks of recurrence, the complexity of surgery, and the need for adjuvant therapy, this paper further supports the management of TGCT in a tertiary referral multi-disciplinary orthopaedic oncology service.Cite this article: Bone Jt Open 2023;4(11):846–852.

The Knee Tenosynovial Giant Cell Tumor: A Deceptive Case Report with Non-Specific Presentations

Background: Tenosynovial giant cell tumor (TGCT) is a rare hyperplastic disease of the synovial membrane of the joint with a high recurrence rate and tumor-like features, affecting large joints such as the hip, knee, and ankle. Dull and chronic pain is common, as is swelling of the joint, which can make definitive diagnosis difficult. The gold standard of treatment is complete resection of the lesion. In this case report, we present a TGCT at the knee joint of an adult patient with nonspecific clinical presentation.
 Case Report: We present a 33-year-old male patient who presented with chronic swelling, warm sensation, and limited range of motion (ROM) in the knee. He had no history of trauma and infectious disease had been ruled out. After several nonspecific orthopedic procedures and inadequate treatment of signs and symptoms, he was finally diagnosed with local TGCT.
 Conclusion: To make the correct diagnosis, the unusual and somehow deceptive clinical presentation of TGCT must be considered.

Pigmented Villonodular Synovitis in a 15-Month-Old Boy Challenged the Physicians for Two Years: A Case Report and Literature Review

Background: Pigmented villonodular synovitis (PVNS) is a very rare pathology of the synovial membrane and even less common in the pediatric group. Rarity leads to misdiagnosis in pre-puberty cases, which may waste significant time for the patient before definite treatment. Reviewing such cases is useful for every pediatrician or orthopedic surgeon to avoid misdiagnosing possible cases.
 Case Report: We report a 15-month-old boy who suffered pain and swelling in his knee for about two years before he was eventually diagnosed with PVNS and underwent surgery. Keeping this diagnosis in mind may have saved him and his family from two years of pain, several admissions, and unnecessary prescriptions.
 Conclusion: PVNS in pediatrics is rare, but it can occur and be misdiagnosed for diseases such as juvenile rheumatoid arthritis (JRA) and septic arthritis which elongates the pain period. PVNS responds well to subtotal synovectomy, and symptoms are relieved after the surgery if well performed.