Pathology of intra-articular tumours and tumour-like lesions: pearls, pitfalls and rarities from a general surgical pathology practice

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.

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

PURPOSE

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.

RESULT

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.

CONCLUSION

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.

MRI of diffuse-type tenosynovial giant cell tumour in the knee: a guide for diagnosis and treatment response assessment

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.

The effect of Imatinib Mesylate in diffuse-type Tenosynovial Giant Cell Tumours on MR imaging and PET-CT

INTRODUCTION

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.

MATERIALS AND 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.

CONCLUSION

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.

Risk factors for early osteoarthritis in tenosynovial giant cell tumour

OBJECTIVE

Tenosynovial giant cell tumour (TGCT) is locally aggressive entity affecting young people (around 4^th 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.

MATERIAL AND 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.

Pigmented villonodular synovitis of the knee: A retrospective analysis of 214 cases at a UK tertiary referral centre

AIMS

Pigmented villonodular synovitis (PVNS) is a rare, locally aggressive and potentially recurrent synovial disease. We present the largest single-centre experience of knee PVNS. Our aim was to evaluate our tertiary hospital's experience in the management of knee PVNS.

PATIENTS AND METHODS

Retrospective data collection of consecutive cases of knee PVNS from 2002 to 2015.

RESULTS

In total, 214 cases of knee PVNS were identified which represented 53.4% of all PVNS (12.1% were recurrent at presentation). 100 were localised PVNS (LPVNS), 114 diffuse PVNS (DPVNS) and two malignant PVNS. Knee PVNS was more likely to occur in females with a mean age of 39. Following surgery, 47.6% had recurrence with DPVNS as opposed to 8.6% with LPVNS. In LPVNS, there was no significant difference in recurrence between open and arthroscopic synovectomy (8.7% vs 9.1%, P>0.05). However, in DPVNS, there was a significantly higher risk of recurrence with arthroscopic compared to open synovectomy (83.3% vs 44.8%, RR=1.86 95% CI 1.32-2.62, P=0.0004).

CONCLUSION

PVNS can be difficult to treat. We found no difference in local recurrence rates between open and arthroscopic treatment of LPVNS but significantly increased rates of recurrence for DPVNS following arthroscopic treatment. We would therefore recommend open synovectomy for DPVNS.

Combined arthroscopic and open synovectomy for diffuse pigmented villonodular synovitis of the knee

PURPOSE

There are few reports detailing recurrence rates or functional outcomes after combined arthroscopic and open synovectomy to treat diffuse pigmented villonodular synovitis (DPVNS) of the knee.

METHODS

Patients with DPVNS of the knee treated with combined synovectomy, followed for a minimum of 12 months at a tertiary orthopaedic oncology centre, were identified. We extracted data pertaining to demographics, complications, clinical outcomes and recurrence. Functional status was evaluated prospectively using the Toronto Extremity Salvage Score (TESS) and the Musculoskeletal Tumor Society (MSTS) 1987 and 1993 surveys. Data were reported descriptively as mean (SD) unless otherwise specified.

RESULTS

Fifteen patients [80% female; mean age 38.9 (SD 14.2) years] representing 15 knees were treated with combined synovectomies and followed for 81 (SD 55) months. Posterior arthroscopy was utilized in 73% of patients. External beam radiation was utilized post-operatively in 73% of patients. Two patients (13%) experienced symptomatic disease recurrence. The mean post-operative knee range of motion was 1° (range 0-10°) to 115° (range 90-135°). TESS and MSTS 1987/1993 scores all suggested excellent patient function. Post-operative complications included one posterior wound dehiscence, one case of femoral condyle avascular necrosis and one patient with lymphedema.

CONCLUSIONS

Combined synovectomy resulted in a low rate of symptomatic disease recurrence and good to excellent functional outcomes for diffuse PVNS of the knee. A literature review identified this as largest case series focusing on combined synovectomies for DPVNS of the knee and the only one describing functional outcomes or the use of external beam radiotherapy.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

Tenosynovial giant cell tumour (pigmented villonodular synovitis-)-like changes in periprosthetic interface membranes

Tenosynovial giant cell tumour (TSGCT; synonym, pigmented villonodular synovitis (PVNS)) is a rare low-grade mesenchymal neoplasm of either intra-articular or extra-articular origin. The etiopathogenesis of TSGCT is still uncertain, but recent studies showed a translocation involving colony-stimulating factor 1 (CSF-1) gene in a subset of cases. Histological features mimicking TSGCT can sometimes be encountered in periprosthetic interface membranes. To investigate the frequency and morphologic spectrum of this phenomenon, we conducted a systematic analysis of 477 periprosthetic interface membranes and performed immunohistochemical analysis on a subset of lesions compared to genuine TSGCT. In 26 of 477 periprosthetic membrane samples (5 %), at least some TSGCT-like features were found and 18 cases (4 %) strongly resembled it. Wear particles were detected in 100 % of the TSGCT-like lesions but only in 63.3 % of the whole cohort of periprosthetic membranes (p value <0.001). Immunohistochemistry comparing true TSGCT and TSGCT-like membranes showed similar inflammatory infiltrates with slightly elevated CD3+/CD8+ T lymphocytes and a slightly higher proliferation index in TSGCT samples. In conclusion, TSGCT-like changes in periprosthetic membranes likely represent exuberant fibrohistiocytic inflammatory response induced by wear particles and should be distinguished from genuine (neoplastic) TSGCT. Although TSGCT and TSGCT-like periprosthetic membranes represent different entities, their comparable morphology might reflect analogous morphogenesis.

Tenosynovial giant cell tumour/pigmented villonodular synovitis: outcome of 294 patients before the era of kinase inhibitors

BACKGROUND

Tenosynovial giant cell tumour/pigmented villonodular synovitis (TGCT/PVNS) is a benign neoplasm of synovium and tendon sheath. We conducted a retrospective pooled analysis in three major referral centers.

METHODS

Patients treated between 1998 and 2008 were examined. Only patients presenting with primary disease or first relapse were included. 5-year local failure free survival (5-year-LFFS) was analysed.

RESULTS

294 patients were included: 254 with new diagnosis and 40 in 1st local recurrence (171 F/123 M; median age: 36 years; tumour size ⩽2 cm in 27% of patients, >2 to ⩽5 cm in 41%, and >5 cm in 32%). A diffuse pattern was reported in 69%, localised in 31%. No metastases were documented. Local failure (LF) was reported in 28% of patients: 36% in diffuse pattern, 14% in localised (p = 0.002); median time to LF: 16 months. With a median follow-up of 4.4 years, 5-year-LFFS was 66%, with multiple (up to five) local recurrences in 40% of relapsed patients. Size <2 cm, macroscopically complete resection, female gender and new diagnosis were associated with a better local control. After multivariate analysis, a previous relapse was independently associated with local failure.

CONCLUSIONS

This study underlines the propensity of TGCT/PVNS to multiple local recurrences. In absence of clinical factors, biological studies are needed to identify prognostic factors of local failure. After a first local recurrence, surgery does not seem to have a curative potential. In these high risk patients, studies addressing the role of target therapies are needed.

Tenosynovial giant cell tumour of brachial plexus

Tenosynovial giant cell tumours (TGT) are benign tumours that arise in the synovial lining of joints, tendon sheaths and bursae. Tumours arising from the vertebral column are extremely rare, with few cases reported. In this article, we describe an unusual case of an extra-articular TGT of the brachial plexus, arising from the synovium of the vertebral facet joint. To our knowledge and after a review of the literature, this is the first patient with a TGT involving the brachial plexus. The clinical, radiological and histological features of this tumour are described together with a brief discussion of management options.

Postsurgical paracicatricial cutaneous satellitosis of giant cell tumour of the tendon sheath, localized type

Tenosynovial giant cell tumour (localized type) is a tumour of tendon sheaths and interphalangeal joints, affecting the digits and arising from the synovium. It is characterized by a proliferation of mononuclear cells and osteoclast-like polykaryocytes. Its propagation to the skin is an exceptional event, which can take place either in localized form in the fingertips (localized type) or in the rare diffuse form called giant cell tumour of the tendon sheath (diffuse type). We report here a case of giant cell tumour with cutaneous satellites, which appeared close to and around the surgical scar following the excision of the primary lesion, in a 9-year-old boy. In the cutaneous satellites, a few signs of transformation could be observed, consisting of the lack of stroma and pronounced cellularity characterized by sheets of rounded synovial-like cells admixed with multinucleated giant cells and xanthoma cells. No relapse was observed 1 year after a plastic surgery procedure (complete replacement of the involved skin). Diffuse lesions usually represent a diagnostic problem in comparison with their localized counterparts. The malignant transformation of an originally typical tenosynovial giant cell tumour is a rare but well-documented event. Our case seems to represent a typical example because the pronounced cellularity might wrongly lead to a diagnosis of malignancy.