Intra-articular tumours are uncommonly encountered in routine practice and may present diagnostic challenges to pathologists. Challenges unique to this site include distinction from more common reactive synovial conditions, which are far more common; histologic variability; superimposed reactive changes; and often, lack of provided clinicoradiological context. This article reviews the pathology of the synovial tumours and tumour-like lesions, including diagnostic pearls, pitfalls and rare entities.

Tenosynovial giant cell tumour (TGCT), previously called pigmented villonodular tenosynovitis (PVNS), is a rare benign, locally aggressive condition that primarily affects the synovial lining of large joints, such as the knee, the hip, and the ankle. TGCT of the hip joint is a relatively scarce entity, and its diagnosis is often challenging. This article reports a case of TGCT affecting the left acetabulum, the left femoral head, and the ligamentum teres of the hip joint in a 39-year-old woman who presented to our clinic three months after the onset of symptoms. The patient underwent a biopsy, computer tomography (CT), and magnetic resonance imaging (MRI). All tests were inconclusive. Total hip arthroplasty (THA) was subsequently performed, leading to healing of the lesion previously present. Following surgery, a second biopsy classified this lesion as TGCT. By sharing our experience with this rare manifestation, we aim to contribute to the growing body of knowledge on the diagnosis and management of TGCT, specifically when it occurs in the hip joint.

OBJECTIVE: Tenosynovial 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.
METHODS: Two 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.
RESULTS: 22 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.
CONCLUSIONS: MMP9, 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.

Pigmented villonodular synovitis (PVNS) is a rare benign condition of tenosynovial proliferation that mostly affects the knee joint. In this case report, we present a 39-year-old female with a ten-year history of gradual progression in the size of painful soft tissue swelling in her left knee. Our case report emphasizes the MRI\'s ability to provide detailed information on tendon sheath and synovium involvement, as well as extensive extra-articular involvement and hemosiderin deposition.

Tenosynovial giant cell tumor (TGCT) is a benign proliferative disease affecting synovial membranes. There are 2 forms, localized (L-TGCT) and diffuse (D-TGCT), which although histologically similar behave differently. It is locally invasive and is treated in most cases by operative excision. The aim of this study was to assess current practice, how the patients\' presentation affected their outcome, as well as review the recurrence rates and complications.
A retrospective analysis of 123 cases was performed in patients treated between 2003 and 2019 with TGCT of the foot and/or ankle. Data were collected on age at presentation, radiologic pattern of disease, location of disease, treatment provided, and recurrence rates. The minimum follow-up was 2 years with a mean of 7.7 years.
There were 61.7% female patients with a mean age of 39 (range, 11-76) years. L-TGCT accounted for 85 (69.1%) cases and D-TGCT for 38 (30.9%). The most prevalent preoperative symptoms were a palpable mass (78/123) and pain (65/123). Radiologically confirmed recurrence in the operative group was noted in 14.5% (16/110) cases. This comprised 4% (3/75) of operatively treated L-TGCT and 37% (13/35) of operatively treated D-TGCT. Patients with pain on presentation and those with erosive changes on presenting magnetic resonance imaging (MRI) were more likely to have persistent postoperative pain (P < .001 for both). Where patients had both preoperative pain and erosive changes, 57.1% had postoperative pain. Thirteen cases were managed nonoperatively where symptoms were minimal, with 1 case requiring surgery at a later date.
Outcomes of TGCT management are dependent on the disease type, extent of preoperative erosive changes, and presence of preoperative pain. These data are useful for counseling patients regarding the outcomes of surgical intervention and help guide the timing of intervention.
Level III, retrospective cohort study.

Tenosynovial giant cell tumour (TGCT) is a rare soft-tissue tumour originating from synovial lining of joints, bursae and tendon sheaths. The tumour comprises two subtypes: the localised-type (L-TGCT) is characterised by a single, well-defined lesion, whereas the diffuse-type (D-TGCT) consists of multiple lesions without clear margins. D-TGCT was previously known as pigmented villonodular synovitis. Although benign, TGCT can behave locally aggressive, especially the diffuse-type. Magnetic resonance imaging (MRI) is the modality of choice to diagnose TGCT and discriminate between subtypes. MRI can also provide a preoperative map before synovectomy, the mainstay of treatment. Finally, since the arrival of colony-stimulating factor 1-receptor inhibitors, a novel systemic therapy for D-TGCT patients with relapsed or inoperable disease, MRI is key in assessing treatment response. As recurrence after treatment of D-TGCT occurs more often than in L-TGCT, follow-up imaging plays an important role in D-TGCT. Reading follow-up MRIs of these diffuse synovial tumours may be a daunting task. Therefore, this educational review focuses on MRI findings in D-TGCT of the knee, which represents the most involved joint site (approximately 70% of patients). We aim to provide a systematic approach to assess the knee synovial recesses, highlight D-TGCT imaging findings, and combine these into a structured report. In addition, differential diagnoses mimicking D-TGCT, potential pitfalls and evaluation of tumour response following systemic therapies are discussed. Finally, we propose automated volumetric quantification of D-TGCT as the next step in quantitative treatment response assessment as an alternative to current radiological assessment criteria.

暂无摘要。

BACKGROUND: Recurrence rates remain high after surgical treatment of diffuse-type Tenosynovial Giant Cell Tumour (TGCT). Imatinib Mesylate (IM) blocks Colony Stimulating Factor1 Receptor (CSF1R), the driver mechanism in TGCT. The aim of this study was to determine if IM reduces the tumour metabolic activity evaluated by PET-CT and to compare this response with the response seen on MR imaging.
METHODS: 25 Consecutive patients treated with IM (off label use) for locally advanced (N = 12) or recurrent (N = 13) diffuse-type TGCT were included, 15 male and median age at diagnosis 39 (IQR 31-47) years. The knee was most frequently affected (n = 16; 64%). The effect of IM was assessed pre- and post-IM treatment by comparing MR scans and PET-CT. MR scans were assessed by Tumour Volume Score (TVS), an estimation of the tumour volume as a percentage of the total synovial cavity. PET-CT scans were evaluated based on maximum standardized uptake value (SUV-max). Partial response was defined as more than 50% tumour reduction with TVS and a decrease of at least 30% on SUV-max.
RESULTS: Median duration of IM treatment was 7.0 (IQR 4.2-11.5) months. Twenty patients (80%) discontinued IM treatment for poor response or intended surgery. Twenty patients experienced an adverse event grade 1-2, three patients grade 3 (creatinine increment, neutropenic sepsis, liver dysfunction). MR assessment of all joints showed 32% (6/19) partial response and 63% (12/19) stable disease, with a mean difference of 12% (P = 0.467; CI -22.4-46.0) TVS between pre- and post-IM and a significant mean difference of 23% (P = 0.021; CI 4.2-21.6) in all knee lesions. PET-CT, all joints, showed a significantly decreased mean difference of 5.3 (P = 0.004; CI 1.9-8.7) SUV-max between pre- and post-IM treatment (58% (11/19) partial response, 37% (7/19) stable disease). No correlation between MR imaging and PET-CT could be appreciated in 15 patients with complete radiological data.
CONCLUSIONS: This study confirms the moderate radiological response of IM in diffuse-type TGCT. PET-CT is a valuable additional diagnostic tool to quantify response to tyrosine kinase inhibitor treatment. Its value should be assessed further to validate its efficacy in the objective measurement of biological response in targeted systemic treatment of TGCT.

Pexidartinib is the first approved medication in the USA for people with tenosynovial giant cell tumor (TGCT). The drug was approved based on the ENLIVEN study, which looked at pexidartinib (brand name, Turalio™), a medication taken by mouth (orally) for people with TGCT (also known as giant cell tumor of the tendon sheath [GCTTS] and pigmented villonodular synovitis [PVNS]) who are not able to have surgery because of the location and/or the size of the tumor. The study showed that pexidartinib is effective in treating people with TGCT because it shrunk the size of their tumors and improved their symptoms and their ability to function. In general, people treated with pexidartinib had side effects that were mostly mild that went away after treatment with pexidartinib was stopped. The most common side effects were hair color changes and tiredness (fatigue). Pexidartinib was also associated with liver problems (or hepatotoxicity), which started within the first 2 months of treatment. Due to the risk of liver problems, which may be severe and potentially life threatening, the researchers closely monitored participants\' blood liver function tests before, during, and after participants in the study took pexidartinib. To read the full Plain Language Summary of this article, click on the View Article button above and download the PDF. Clinical Trial Registration: NCT02371369 (ClinicalTrials.gov).

OBJECTIVE: Tenosynovial giant cell tumour (TGCT) is locally aggressive entity affecting young people (around 4th decade of life) and can cause joint destruction. It could be nodular or diffuse. These two varieties are histological and genetically similar, but present a different prognosis. The aim of this study is to identify risk factors for local recurrence and predisposing factors for the development of early osteoarthritis in patients with TGCT.
METHODS: We conducted a retrospective study of 35 patients with an anatomopathological diagnosis of TGCT in our Institution from 1991 to 2017. The mean follow-up was 8.2 years. Demographic variables, characteristics of the primary tumor and its evolution were collected to assess the risk factors for local recurrence and early osteoarthritis.
RESULTS: The diffuse type was identified as a risk factor for the development of osteoarthritis (p=0.01) and for local recurrence (p=0.015). Osteoarthritis was more frequent in the hip and ankle than in the knee (p=0.03). A difference of 16 months in the duration of symptoms prior to diagnosis between those who developed osteoarthritis and those who did not was observed (p=0.05).
CONCLUSIONS: The diffuse type is more aggressive than the nodular type; it is associated with a higher risk of osteoarthritis and local recurrence. The hip and ankle present a higher risk of osteoarthritis than other joints. The time of evolution of the symptoms before diagnosis and adequate treatment, negatively influences the development of osteoarthritis.