A molecular study of synovial chondromatosis

Updates in non-neoplastic orthopaedic pathology: what you don't know can hurt you!

Even though the average surgical pathologist reviews far more non-neoplastic orthopaedic pathology on a daily basis, most current research focuses on rare tumours and their even less frequent molecular events. Our experiences among consults and focused conferences strongly suggest that there remains a practice gap regarding knowledge and diagnosing specific non-neoplastic orthopaedic conditions. One of the most frequent intraoperative consultations performed in the USA, among both academic and private institutions, relates to revision arthroplasty and the determination of infection in periprosthetic joints. Pathologists play a critical role in this algorithm, helping determine intraoperatively whether patients require antibiotic spacers prior to reimplantation. Many pathology departments have abandoned the examination of arthroplasty specimens because they (and their surgeons) mistakenly believe there is little clinically relevant information to be gained by thorough pathological examination. However, recent literature has challenged this concept, emphasising the importance of distinguishing avascular necrosis (from osteoarthritis/degenerative joint disease with secondary osteonecrosis), subchondral insufficiency fracture, septic arthritis (from so-called 'sterile' osteomyelitis/pseudoabscesses), underlying crystalline diseases and incidental/occult neoplasia. Histological evaluation of historically insignificant orthopaedic specimens, such as tenosynovium from carpal tunnel syndrome/trigger finger, is now seen as valuable in early diagnosis of cardiac amyloidosis. Not infrequently, orthopaedic conditions like haemosiderotic synovitis, osteocartilaginous loose bodies or rheumatoid nodules, may histologically mimic bona fide neoplasms, notably diffuse tenosynovial giant cell tumour, synovial chondromatosis and epithelioid sarcoma, respectively. Here is a review of the more common non-neoplastic orthopaedic conditions, those likely to be examined by the practising surgical pathologist, with updates and guidelines for establishing clinically relevant diagnoses.

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.

Clinical guidance based on MRI for the management of temporomandibular joint synovial chondromatosis: One institution's experience

The aim of this retrospective observational study was to introduce a comprehensive MRI evaluation criterion for the clinical management of synovial chondromatosis of the temporomandibular joint (TMJ-SC). Patients received different treatments according to the MRI evaluation system: bone erosion, extent, articular disc condition, location, maturity, and size of loose body. At least a 2-year follow-up was completed to assess tumor recurrence, visual analogue scale score for pain (VAS) and maximum interincisal opening (MIO). Of the 195 patients included for TMJ-SC, 34 received arthroscopy and 161 received open surgery. Among the patients with significant extent of SC, 32 received temporary resection of the condylar neck or zygomatic arch and 2 received treatment combined with ear, nose and throat(ENT). 28 received articular disc reconstruction and 56 received disc repositioning. Patients showed good recovery of joint function with only two cases of tumor recurrence at an average follow-up of 75.1 months after surgery. The MIO had improved from 30.2 mm to 40.0 mm(P < 0.0001) and VAS had decreased from 5.1 to 0.78(P < 0.0001).The preoperative MRI evaluation principles has been effective in selecting appropriate surgical options.

Comprehensive Molecular Characterization of a Large Series of Calcified Chondroid Mesenchymal Neoplasms Widening Their Morphologic Spectrum

Recently, FN1 fusions to receptor tyrosine kinase genes have been identified in soft tissue tumors with calcified chondroid matrix named calcifying chondroid mesenchymal neoplasms (CCMNs). We collected 33 cases of CCMN from the French network for soft tissue and bone tumors. We performed whole-exome RNA sequencing, expression analysis, and genome-wide DNA methylation profiling in 33, 30, and 20 cases of CCMN compared with a control group of tumors, including noncalcified tenosynovial giant cell tumor (TGCT). Among them, 15 cases showed morphologic overlap with soft tissue chondroma, 8 cases with tophaceous pseudogout, and 10 cases with chondroid TGCT. RNA-sequencing revealed a fusion of FN1 in 76% of cases (25/33) with different 5' partners, including most frequently FGFR2 (14 cases), TEK or FGFR1. Among CCMN associated with FGFR1 fusions, 2 cases had overexpression of FGF23 without tumor-induced osteomalacia. Four CCMN had PDGFRA::USP8 fusions; 3 of which had histologic features of TGCT and were located in the hip, foot, and temporomandibular joint (TMJ). All cases with FN1::TEK fusion were located at TMJ and had histologic features of TGCT with or without chondroid matrix. They formed a distinct cluster on unsupervised clustering analyses based on whole transcriptome and genome-wide methylome data. Our study confirms the high prevalence of FN1 fusions in CCMN. In addition, through transcriptome and methylome analyses, we have identified a novel subgroup of tumors located at the TMJ, exhibiting TGCT-like features and FN1::TEK fusions.

CD34+ synovial fibroblasts exhibit high osteogenic potential in synovial chondromatosis

Synovial chondromatosis (SC) is a disorder of the synovium characterized by the formation of osteochondral nodules within the synovium. This study aimed to identify the abnormally differentiated progenitor cells and possible pathogenic signaling pathways. Loose bodies and synovium were obtained from patients with SC during knee arthroplasty. Single-cell RNA sequencing was used to identify cell subsets and their gene signatures in SC synovium. Cells derived from osteoarthritis (OA) synovium were used as controls. Multi-differentiation and colony-forming assays were used to identify progenitor cells. The roles of transcription factors and signaling pathways were investigated through computational analysis and experimental verification. We identified an increased proportion of CD34+ sublining fibroblasts in SC synovium. CD34+CD31- cells and CD34-CD31- cells were sorted from SC synovium. Compared with CD34- cells, CD34+ cells had larger alkaline phosphatase (ALP)-stained area and calcified area after osteogenic induction. In addition, CD34+ cells exhibited a stronger tube formation ability than CD34- cells. Our bioinformatic analysis suggested the expression of TWIST1, a negative regulator of osteogenesis, in CD34- sublining fibroblasts and was regulated by the TGF-β signaling pathway. The experiment showed that CD34+ cells acquired the TWIST1 expression during culture and the combination of TGF-β1 and harmine, an inhibitor of Twist1, could further stimulate the osteogenesis of CD34+ cells. Overall, CD34+ synovial fibroblasts in SC synovium have multiple differentiation potentials, especially osteogenic differentiation potential, and might be responsible for the pathogenesis of SC.

Loose Bodies Found in the Human Intra-Articular Space Showed Characteristics Similar to Endochondral Bone Formation

OBJECTIVE

Loose bodies are free-floating tissues of cartilage and bone that can cause pain, swelling, the inability to straighten the knee, or intermittent locking of the knee. Loose bodies can arise from degenerative joint disease, flake fractures, osteochondritis dissecans, or chondromatosis. We hypothesized that loose bodies can be classified in stages with tissue characteristics similar to endochondral ossification.

DESIGN

Loose bodies were harvested from patients undergoing joint replacement. Samples were processed for histology, gene expression analysis, and micro-computed tomography (µCT). Cartilage- and bone-related genes and proteins were selected for immunofluorescence stainings (collagen type I, II, and X, SOX9 [SRY-box transcription factor 9], and MMP13 [matrix metalloproteinase 13]) and gene expression analysis (FN [fibronectin], COL1A1, COL2A1, COL10A1, SOX9, MMP13, and aggrecan [ACAN]).

RESULTS

Loose bodies were grouped in 4 stages: fibrous, (mineralized) cartilaginous, cartilage and bone, and bone. Hyaline-like cartilage tissue with Benninghoff arcades was present in stages 2 and 3. A transition from cartilaginous to mineralized tissue and bone trabecula was defined by an increase in COL1A1 and COL10A1 (stage 3 vs. 4: p = 0.047) positive area. Stage 4 showed typical trabecular bone tissue. The relative volume of calcified tissue (mineralized cartilage and bone tissue) decreased with stages (stages 1-2 vs. 3: p = 0.002; stage 1-2 vs. 4: p = 0.012). COL2A1 expression and stained area decreased from stages 1-2 to 4 (p = 0.010 and p = 0.004). ACAN expression decreased from stage 1-2 to stage 3 (p = 0.049) and stage 4 (p = 0.002).

CONCLUSION

Loose bodies show tissue characteristics similar to endochondral ossification. They are probably a relevant substrate for regenerative therapeutic interventions in joint disease.

Synovial chondromatosis: a case series and review of the literature

This case series reviews 2 patients worked up and treated for unilateral synovial chondromatosis of the temporomandibular joint (TMJ). The first was a 58-year-old female evaluated and treated for synovial chondromatosis of the left TMJ using an arthrotomy of the joint to remove the cartilaginous and osteocartilaginous nodules. The second is a 63-year-old male who was evaluated and treated for synovial chondromatosis of the right TMJ with the removal of extracapsular masses and an arthrotomy with intra-joint removal of nodules. Six-year radiographic follow-up demonstrated no recurrence of the pathology in his case. The cases are reviewed in this article, along with a current review of the literature.

Calcified Chondroid Mesenchymal Neoplasm: Exploring the Morphologic and Clinical Features of an Emergent Entity With a Series of 33 Cases

Calcified chondroid mesenchymal neoplasm is a term proposed for tumors with a spectrum of morphologic features, including cartilage/chondroid matrix formation, that frequently harbor FN1 gene fusions. We report a series of 33 cases of putative calcified chondroid mesenchymal neoplasms, mostly referred for expert consultation out of concern for malignancy. Patients included 17 males and 16 females, with a mean age of 51.3 years. Anatomic locations include the hands and fingers, feet and toes, head and neck, and temporomandibular joint; 1 patient presented with multifocal disease. Radiologic review showed soft tissue masses with variable internal calcification, which occasionally scalloped bone but in all cases appeared indolent/benign. Tumors had a mean gross size of 2.1 cm and a homogenous rubbery to fibrous/gritty tan-white cut surface. Histology demonstrated multinodular architecture with a prominent chondroid matrix and increased cellularity towards the periphery of the nodules. The tumor cells were polygonal with eccentric nuclei and bland cytologic features and showed a variable amount of increased spindled / fibroblastic forms in the perinodular septa. The majority of cases had notable grungy and/or lacy calcifications. A subset of cases demonstrated at least focal areas of increased cellularity and osteoclast-like giant cells. Herein, we confirm the distinct morphologic and clinicopathologic features associated with this entity with the largest series to date, with a focus on practical diagnostic separation from similar chondroid neoplasms. Awareness of these features is critical in avoiding pitfalls, including a malignant diagnosis of chondrosarcoma.

Gene fusions are frequent in ACTH-secreting neuroendocrine neoplasms of the pancreas, but not in their non-pancreatic counterparts

Ectopic Cushing syndrome is a rare clinical disorder resulting from excessive adrenocorticotrophic hormone (ACTH) produced by non-pituitary neoplasms, mainly neuroendocrine neoplasms (NENs) of the lung, pancreas, and gastrointestinal tract, and other less common sites. The genetic background of ACTH-producing NENs has not been well studied. Inspired by an index case of ACTH-producing pancreatic NEN carrying a gene fusion, we postulated that ACTH-producing NENs might be enriched for gene fusions. We herein examined 21 ACTH-secreting NENs of the pancreas (10), lung (9), thymus (1), and kidney (1) using targeted RNA sequencing. The tumors were classified according to the most recent WHO classification as NET-G1/typical carcinoid (n = 4), NETG-2/atypical carcinoid (n = 14), and NET-G3 (n = 3). Overall, targeted RNA sequencing was successful in 11 cases (4 of 10 pancreatic tumors, 5 of 9 pulmonary tumors, and in the one renal and one thymic tumor). All four successfully tested pancreatic tumors revealed a gene fusion: two had a EWSR1::BEND2 and one case each had a KMT2A::BCOR and a TFG::ADGRG7 fusion, respectively. EWSR1 rearrangements were confirmed in both tumors with a EWSR1::BEND2 by FISH. Gene fusions were mutually exclusive with ATRX, DAXX, and MEN1 mutations (the most frequently mutated genes in NETs) in all four cases. Using RNA-based variant assessment (n = 16) or via the TSO500 panel (n = 5), no pathogenic BCOR mutations were detected in any of the cases. Taken together, gene fusions were detected in 4/4 (100%) pancreatic versus 0/7 (0%) non-pancreatic tumors, respectively. These results suggest a potential role for gene fusions in triggering the ACTH production in pancreatic NENs presenting with ectopic Cushing syndrome. While the exact mechanisms responsible for the ectopic ACTH secretion are beyond the scope of this study, overexpressed fusion proteins might be involved in promoter-mediated overexpression of pre-ACTH precursors in analogy to the mechanisms postulated for EWSR1::CREB1-mediated paraneoplastic phenomena in certain mesenchymal neoplasms. The genetic background of the ACTH-producing non-pancreatic NENs remains to be further studied.

Management of temporomandibular joint diseases: a rare case report of coexisting calcium pyrophosphate crystal deposition and synovial chondromatosis

BACKGROUND

The coexistence of calcium pyrophosphate dihydrate crystal deposition (CPP) and synovial chondromatosis (SC) in the temporomandibular joint (TMJ) is rarely reported. CPP disease (CPPD) is complex arthritis synonymous with excessive pyrophosphate production and variable aberrations in mineral and organic phase metabolism of the joint cartilage, leading to local inundated CPP and crystal deposition of partially deciphered predispositions. Meanwhile, SC is a rare benign synovial joint proliferative disease of unclear etiology and has a low risk of malignant transformation. However, SC manifests severe joint disability and dysfunction because of connective tissue metaplasia of the synovial membrane, which forms cartilaginous nodules with or without calcifications or ossifications. These nodules often detach and form intra-articular loose bodies and very rarely within extraarticular spaces.

CASE PRESENTATION

We report the case of a 61-year-old man to expand the body of literature on these unusual coexisting arthropathies of the TMJ. The patient presented to our hospital in 2020 with complaints of pain in the right TMJ and trismus for over 6 months. Radiographic assessments of the TMJ provided a preoperative provisional diagnosis of SC. However, the histopathology of the open biopsy revealed tumor-like lesions comprising several deposits of rhomboid and rod-shaped crystals that displayed positive birefringence in polarized light, confirming a coexistence of CPPD. A second-stage operation was performed for the complete removal of the loose bodies and chalk-like lesions including synovectomy. No evidence of recurrence was recorded after a follow-up of nearly 1.5 years.

CONCLUSIONS

Isolated CPPD and SC of the TMJ are prevalent in the literature however, monoarticular coexistence of these diseases is rare, due to the lack of consistency in the diagnostic criteria in clinical practice. Moreover, optimal treatment depends on several considerations. This report delineated the molecular etiopathology and underscored the need for continued deciphering of the causal mechanisms of coexisting CPPD and SC of the TMJ. In addition, the importance of confirmatory testing for accurate diagnosis, and appropriate management of these diseases were discussed.

Detection of sarcoma fusions by a next-generation sequencing based-ligation-dependent multiplex RT-PCR assay

Morphological, immunohistochemical, and molecular methods often need to be combined for accurate diagnosis and optimal clinical management of sarcomas. Here, we have developed, a new molecular diagnostic assay, for the detection of gene fusions in sarcomas. This targeted multiplexed next-generation sequencing (NGS)-based method utilizes ligation dependent reverse-transcriptase polymerase chain reaction (LD-RT-PCR-NGS) to detect oncogenic fusion transcripts involving 137 genes, leading to 139 gene fusions known to be recurrently rearranged in soft-tissue and bone tumors. 158 bone and soft-tissue tumors with previously identified fusion genes by fluorescent in situ hybridization (FISH) or RT-PCR were selected to test the specificity and the sensitivity of this assay. RNA were extracted from formalin-fixed paraffin-embedded (n = 143) or frozen (n = 15) material (specimen; n = 42 or core needle biopsies; n = 116). Tested tumors encompassed 23 major translocation-related sarcomas types, including Ewing and Ewing-like sarcomas, rhabdomyosarcomas, desmoplastic small round-cell tumors, clear-cell sarcomas, infantile fibrosarcomas, endometrial stromal sarcomas, epithelioid hemangioendotheliomas, alveolar soft-part sarcomas, biphenotypic sinonasal sarcomas, extraskeletal myxoid chondrosarcomas, myxoid/round-cell liposarcomas, dermatofibrosarcomas protuberans and solitary fibrous tumors. In-frame fusion transcripts were detected in 98.1% of cases (155/158). Gene fusion assay results correlated with conventional techniques (FISH and RT-PCR) in 155/158 tumors (98.1%). These data demonstrate that this assay is a rapid, robust, highly sensitive, and multiplexed targeted RNA sequencing assay for the detection of recurrent gene fusions on RNA extracted from routine clinical specimens of sarcomas (formalin-fixed paraffin-embedded or frozen). It facilitates the precise diagnosis and identification of tumors with potential targetable fusions. In addition, this assay can be easily customized to cover new fusions.

Primäre synoviale Chondromatose

Hintergrund

Die primäre synoviale Chondromatose (SC) ist eine seltene Erkrankung der Synovialmembran unklarer Ätiologie. Der aktuelle Wissensstand zu dieser Erkrankung soll in einer kurzen Übersicht dargestellt werden.

Methoden

Übersichtsarbeiten und rezente Fallberichte zur SC wurden systematisch ausgewertet und mit Daten eigener Fälle in Kontext gesetzt.

Ergebnisse

Auf Grund neuer genomischer Daten wird die SC als benigne Neoplasie eingestuft. In 60 % der Fälle liegen Mutationen im Fibronektin-1-Gen (FN1) und/oder im Gen für den Activin-A-Typ-II-Rezeptor (ACVR2A) vor. Diagnoseweisend ist die Magnetresonanztomographie (MRT) und die meist arthroskopische Biopsie der Synovia. An einem Fallbeispiel soll gezeigt werden, dass die Knorpelaggregate der SC radiologisch nicht immer schattengebend sein müssen. Differenzialdiagnostisch kommen Monarthritiden anderer Ursachen, andere Gelenk- und Muskelerkrankungen mit Mineralisierung sowie weitere von der Synovialmembran ausgehende Erkrankungen in Betracht. Die Entartungsrate liegt bei 2–4 %. Therapeutisch hat sich in den letzten Jahren das arthroskopische Vorgehen durchgesetzt, das an die Ausdehnung der Erkrankung adaptiert wird.

Schlussfolgerung

Genomische Untersuchungen sowie Fallserien und Fallberichte aus jüngerer Zeit werfen ein neues Licht auf die SC. Therapeutisch wird in jüngeren Arbeiten überwiegend arthroskopisch vorgegangen.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Soft Tissue Tumors

The fifth (5th) edition of the World Health Organization (WHO) Classification of Head and Neck Tumors introduces a new chapter dedicated to soft tissue neoplasms commonly affecting the head and neck. While the diversity, rarity, and wide anatomic range of soft tissue tumors precludes a discussion of all entities that may be found in the head and neck, the addition of this new chapter to the head and neck "blue book" aims to provide a more comprehensive and uniform reference text, including updated diagnostic criteria, of mesenchymal tumor types frequently (or exclusively) arising at head and neck sites. Since publication of the previous edition in 2017, there have been numerous advances in our understanding of the pathogenesis of many soft tissue tumors which have facilitated refinements in tumor classification, identification of novel entities, development of diagnostic markers, and improved prognostication. This review will provide a focused discussion of the soft tissue tumors included in the 5th edition WHO Head and Neck classification, with an emphasis on updates.

[Soft tissue tumours with FN1 (Fibronectin 1) fusion gene]

Translocations involving FN1 gene have been described in several tumours, which share the presence of a cartilaginous matrix with or without calcifications and a good prognosis. They encompass: soft tissue chondroma, synovial chondromatosis, calcifying aponeurotic fibroma, phosphaturic mesenchymal tumour and a new spectrum of tumours: "the calcified chondroid mesenchymal neoplasms". We review all the clinical, histopathological and molecular data of these tumours and discuss the differential diagnoses.

Imaging features of cartilaginous tumors of the head and neck

There is a wide spectrum of head and neck cartilaginous lesions which include both neoplastic and nonneoplastic processes. Cartilaginous tumors of the head and neck are uncommon, posing a diagnostic challenge. Benign cartilaginous tumors that may occur in the head and neck include chondroma, chondroblastoma, chondromyxoid fibroma, osteochondroma, and synovial chondromatosis. Chondromesenchymal hamartoma is a rare non-neoplastic cartilaginous lesion that is included for the 1first time in the new WHO classification and radiologically can mimic a tumor. Malignant cartilaginous tumors include chondrosarcoma and chondroid variant of chordoma. Characteristic tumor locations, internal chondroid matrix calcification, and typical T2 hyperintense signal secondary to high-water content within the extracellular matrix of the hyaline cartilage are useful imaging features that narrow the differential diagnosis and help in diagnosing these diseases. This article presents a narrative review of the anatomy of the head and neck cartilaginous structures, discusses the current knowledge and imaging spectrum of benign and malignant cartilaginous tumors and tumor-like lesions of the head and neck.

Intra-Articular Tumors

The intra-articular space is a relatively rare site of occurrence of neoplastic diseases. The 2 distinct groups of clinicopathologic entities that exhibit an almost exclusive tropism for the joints are represented by synovial chondromatosis and tenosynovial giant cell tumors (TGCT). Synovial chondromatosis is a locally aggressive chondrogenic neoplasm that very rarely can show malignant behavior. TGCT occur in 2 main variants, the localized variant and the more locally aggressive diffuse type. Malignant TCGT is exceedingly rare and is characterized by significant rates of both local recurrence and metastatic spread.

Clinical comparison of tenosynovial giant cell tumors, synovial chondromatosis, and synovial sarcoma: analysis and report of 53 cases

Background

Tenosynovial giant cell tumors (TGCTs), synovial chondromatosis (SC), and synovial sarcoma (SS) exhibit similarities in clinical features and histochemical characteristics, and differential diagnosis remains challenging in clinical practice.

Methods

Data were collected from the pathology database of Shanghai Ninth People's Hospital regarding patients who underwent surgery from 2010 to 2019 with histologically confirmed TGCTs, SC, and SS. Demographic and clinicopathological data of these patients were reviewed. Immunohistochemistry staining of 14 different markers was performed. Correlation analyses of the prognoses were evaluated.

Results

A total of 26 patients with TGCTs (8 diffuse TGCTs and 18 localized TGCTs), 16 with SC, and 11 with SS were identified. Pain was the main symptom of patients with both TGCTs and SC, while a palpable mass was the most common symptom for patients with SS. In addition to clinical features, we identified vital risk factors for disease recurrence. The mean follow-up periods were 51, 39, and 14 months for TGCTs, SC, and SS, respectively. Younger patients with diffuse TGCTs or patients with a higher neutrophil/lymphocyte ratio (NLR) displayed a significantly higher frequency of recurrence. We also plotted receiver operating characteristic (ROC) curve analysis for age and NLR. The area under the ROC curve (AUC) was calculated and demonstrated the ability to distinguish recurrent from nonrecurrent cases. In addition, higher CD163 expression was linked to recurrent diffuse TGCT cases.

Conclusions

These data indicated possible characteristics of different aspects of TGCTs, SC, and SS. Further clarification and understanding of these factors will help with differential clinical diagnosis and recurrent risk assessment.

Surgical hip dislocation for treatment of synovial chondromatosis of the hip

PURPOSE

In the present study, we aimed to evaluate the clinical outcomes of surgical hip dislocation in patients with synovial chondromatosis (SC) of the hip.

METHODS

Seven patients with primary SC of the hip treated with open synovectomy and removal of loose bodies by surgical hip dislocation from 2016 to 2019 were retrospectively reviewed. All patients had numerous and widespread loose bodies based on pre-operative images, including routine radiographs, CT, and MRI. The visual analog scale (VAS) score and Harris hip score (HHS) were collected and analyzed before and after surgery. The post-operative radiographs were reviewed to evaluate disease recurrence and osteoarthritis progression.

RESULTS

The mean operative time was 61 minutes (range, 42-75 min). An average of 33 loose bodies in each patient (range, 16-67) was removed, and extra-articular pathology was found in one patient. Patients were followed up for a mean duration of 30 months (range, 18-42 months). The average VAS scores were decreased from 3.7 (range, 2-6) pre-operatively to 0.9 (range, 0-2) at the last follow-up, and the HHS was improved from 60.1 (range, 50-73) to 90.1 (range, 82-95). All results demonstrated significant improvements (P < 0.05). Post-operative radiographs showed no recurrence, osteoarthritis progression, or osteonecrosis of the femoral head in all hips.

CONCLUSIONS

Surgical hip dislocation was a practical approach for managing both intra-articular and extra-articular pathologic lesions around the hip. It was an effective treatment for SC of the hip with short surgical time, good joint functions, a lower recurrence rate, and few complications.

Juvenile Dysplasia Epiphysealis Hemimelica with Multiple Ankle Free Body

Dysplasia epiphysealis hemimelica (DEH), also known as Trevor's disease, is a rare overgrowth of cartilage that commonly arises in the epiphyseal bone of children. We report a rare case of DEH originating from a talus accompanied by multiple intra-articular free bodies in a 7-year-old patient with ankle instability. After the primary surgery for free body removal and microfracture technique for the cartilage defects in the ankle joint, the free body recurred. Secondary surgery of arthroscopic free body removal with lateral ankle ligament repair succeeded in treating the patient, without further recurrence of the free body.

Updates from the 2020 World Health Organization Classification of Soft Tissue and Bone Tumours

The fifth edition of the World Health Organization (WHO) classification of soft tissue and bone tumours was published in May 2020. This 'Blue Book', which is also available digitally for the first time, incorporates an array of new information on these tumours, amassed in the 7 years since the previous edition. Major advances in molecular characterisation have driven further refinements in classification and the development of ancillary diagnostic tests, and have improved our understanding of disease pathogenesis. Several new entities are also included. This review summarises the main changes introduced in the 2020 WHO classification for each subcategory of soft tissue and bone tumours.

Synovial chondrosarcoma: a single-institution experience with molecular investigations and review of the literature

AIMS

To evaluate the available diagnostic histological criteria for synovial chondrosarcoma and to screen for the presence of IDH1/IDH2 mutations in a series of cases of this malignant cartilaginous neoplasm.

METHODS AND RESULTS

Ten cases of synovial chondrosarcoma diagnosed at our institute were reviewed. At presentation, all tumours occurred in adults (median age, 62 years). The most common location was the knee joint (five cases), and the size at diagnosis ranged from 30 mm to 170 mm. Eight patients had secondary synovial chondrosarcomas associated with pre-existing/recurrent or concomitant synovial chondromatosis. Five patients had local recurrences and three had lung metastases. All patients with intralesional excisions developed local recurrences, whereas those who underwent wide resections did not. At last follow-up (mean, 91 months), available for nine patients, seven patients were alive and disease-free, one patient had died of disease, and one was alive with paravertebral metastases. Frequent histological features observed included loss of clustering of chondrocytes (nine cases), the presence of variable amounts of myxoid matrix (eight cases), peripheral hypercellularity (eight cases), tumour necrosis (six cases), and spindling of chondrocytes (four cases). Of the seven cases for which it was possible to evaluate bone permeation, six showed infiltration of bone marrow. All seven cases screened for mutations of exon 4 of IDH1 and IDH2 were found to be wild-type.

CONCLUSIONS

Histological criteria in correlation with clinical and radiological features allow the recognition of synovial chondrosarcoma. IDH1/IDH2 mutations were not present in synovial chondrosarcoma. Adequate surgical margins are important for disease control.

Intraligamentous synovial chondromatosis of the anterior cruciate ligament

Synovial chondromatosis is a rare disease that causes disability and dysfunction of the involved synovial joint. We describe the second case in the literature of intraligamentous synovial chondromatosis involving the anterior cruciate ligament, confirmed by pathology after arthroscopic removal of the chondral bodies. We also describe associated magnetic resonance imaging findings which may be helpful for diagnosis of this very rare entity.