An evaluation of vimseltinib for treatment of tenosynovial giant cell tumors

INTRODUCTION

Tenosynovial giant cell tumor (TGCT) is a rare soft tissue neoplasm with aggressive local growth. The disease is driven by excessive CSF1 expression in tumor cells, leading to increased recruitment of monocytes and macrophages, cytokine production, and tumor development. Targeted therapy against CSF1R is an effective treatment approach for unresectable, symptomatic TGCT. Vimseltinib, a novel, small-molecule tyrosine kinase inhibitor of CSF1R, has shown clinical efficacy in patients with TGCT.

AREAS COVERED

This paper outlines the pathogenesis and therapeutic options for TGCT, along with a detailed profile of vimseltinib, including its mechanism of action, pharmacokinetics, efficacy and safety data from clinical studies. The efficacy and tolerability of vimseltinib are indirectly compared with previously known CSF1R inhibitors.

EXPERT OPINION

In the MOTION study, the use of vimseltinib in patients with advanced TGCT resulted in a high objective response rate, substantial benefit in reducing clinical symptoms (such as pain and stiffness), and a favorable safety profile. Vimseltinib represents a promising new therapeutic option for patients with unresectable TGCT and is currently awaiting regulatory review by the FDA and EMA.

Dermatofibrosarcoma protuberans with PDGFD rearrangements: a case series featuring a novel EMILIN1::PDGFD fusion and comprehensive literature review

Dermatofibrosarcoma protuberans (DFSP) is a locally infiltrative mesenchymal neoplasm usually characterized by a COL1A1::PDGFB fusion. A minority of DFSPs have recently been shown to harbor alternative fusions, involving the PDGFD gene. The aim of this case series and literature review is to highlight the clinicopathologic and molecular features of PDGFD-rearranged DFSPs. Eighteen patients (twelve females and six males) with PDGFD-rearranged DFSPs were collected from the authors' institutional archives. Eight (44%) cases harbored a COL6A3::PDGFD fusion, five (28%) an EMILIN2::PDGFD fusion, and two (11%) an EMILIN1::PDGFD fusion. In three (17%) cases, the fusion partner was unknown. A literature review revealed 29 additional cases. Cumulatively, four alternative fusion genes have been detected: COL6A3::PDGFD (24/47, 51%), EMILIN2::PDGFD (12/47, 26%), EMILIN1::PDGFD (2/47, 4%), and TNC::PDGFD (1/47, 2%). In eight (17%) cases, the fusion partner was unknown. Most (20/24, 83%) COL6A3::PDGFD-fused DFSPs occurred in females with only four (17%) cases described in males. Additionally, half of them (12/24, 50%) developed in the breast/chest wall. EMILIN2::PDGFD-fused DFSPs often occurred in males, were located in the extremities (9/12, 75%), exhibited fibrosarcomatous transformation (9/12, 75%), were confined exclusively or primarily to the subcutis (10/12, 83%), and had a well-circumscribed contour (10/12, 83%). Specific molecular alterations in DFSPs correlate with certain clinicopathologic features. Notably, EMILIN2::PDGFD-fused DFSPs have a slight predilection for males, develop almost exclusively in the subcutis, tend to be well-circumscribed, and often exhibit fibrosarcomatous transformation, while COL6A3::PDGFD-fused DFSPs might have a predilection for the breast/chest wall of female patients. To the best of our knowledge, this is the first report of EMILIN1::PDGFD-fused DFSP.

Treatment of tenosynovial giant tumors with colony-stimulating factor 1 receptor kinase inhibitors: When to start? When to stop? When to restart?

Long‐term treatment of nonresectable tenosynovial giant cell tumor with pexidartinib is feasible and provides long‐term control and symptomatic improvement, with acceptable tolerance. Treatment interruption is possible, and one half of patients remain without progression after interruption. Among those who relapse, pexidartinib is again active, although not all patients need to resume treatment.

Treatment Modalities for Refractory-Recurrent Tenosynovial Giant Cell Tumor (TGCT): An Update

Background and Objectives: Tenosynovial giant cell tumor (TGCT) is a rare, locally aggressive, benign neoplasm arising from the synovium of joints, tendon sheaths, and bursa. There are two main subtypes of TGCT: localized-type TGCT(L-TGCT) and diffuse-type TGCT (D-TGCT). While surgical excision is still considered the gold standard of treatment, the high recurrence rate, especially for D-TGCT, may suggest the need for other treatment modalities. Materials and Methods: This study reviews current literature on the current treatment modalities for refractory-relapsed TGCT disease. Results: The gold standard of treatment modality in TGCT remains surgical excision of the tumor nevertheless, the elevated recurrence rate and refractory disease, particularly in D-TGCT indicates and underscores the necessity for additional treatment alternatives. Conclusions: TGCT is a benign tumor with inflammatory features and a potential destructive and aggressive course that can lead to significant morbidity and functional impairment with a high impact on quality of life. Surgical resection remains the gold standard current treatment and the optimal surgical approach depends on the location and extent of the tumor. Systemic therapies have been recently used for relapsed mainly cases.

Fine-needle aspiration cytology of diffuse type tenosynovial giant cell tumor with malignant trasformation and review of literature

Tenosynovial giant cell tumors (TGCTs) arise from the synovium of joint, bursa, and tendon sheath. Diffuse type often affects large joints, has higher recurrence rates, metastases, and malignant transformation potential compared to the localized type. The cytopathology of TGCT, a fibrohistiocytic neoplasm distinct from other giant cell-rich soft tissue tumors, is rarely reported. Here we describe cytomorphology of a case of TGCT that was initially diagnosed on fine-needle aspiration cytology (FNAC) consisting of a mixture of singly scattered polygonal or spindle mononuclear cells with hemosiderin laden macrophages, inflammatory cells, and a population of multinucleated osteoclast-like giant cells. Persistent symptoms and repeat excision were consistent with high-grade malignant transformation of the TGCT. Atypical cytologic features in a recurrent, infiltrative, or a metastatic lesion should raise suspicion for malignancy.

MANEUVER: A Phase III study of pimicotinib to assess efficacy and safety in tenosynovial giant cell tumor patients

Tenosynovial giant cell tumor (TGCT) is a rare, locally invasive soft tissue tumor arising from the synovium of joints, bursa and tendon sheaths and is associated with the overexpression of the colony-stimulating factor 1 (CSF-1) gene. Pimicotinib is an orally available, highly selective and potent small molecule CSF-1 receptor (CSF-1R) inhibitor with robust efficacy and safety profile in patients with TGCT and is under development in multiple diseases. In an open-label Phase I study in patients with TGCT not amenable to surgery, pimicotinib showed superior efficacy and safety. In this article, we elucidate the rationale and study design of the multi-region Phase III MANEUVER trial (NCT05804045), which is designed to assess the efficacy and safety of pimicotinib in patients with TGCT not amenable to surgical resection in Asia, North America and Europe.

Extensive analysis of 59 sarcoma-related fusion genes identified pazopanib as a potential inhibitor to COL1A1-PDGFB fusion gene

Sarcomas are malignant mesenchymal tumors that are extremely rare and divergent. Fusion genes are involved in approximately 30% of sarcomas as driver oncogenes; however, their detailed functions are not fully understood. In this study, we determined the functional significance of 59 sarcoma-related fusion genes. The transforming potential and drug sensitivities of these fusion genes were evaluated using a focus formation assay (FFA) and the mixed-all-nominated-in-one (MANO) method, respectively. The transcriptome was also examined using RNA sequencing of 3T3 cells transduced with each fusion gene. Approximately half (28/59, 47%) of the fusion genes exhibited transformation in the FFA assay, which was classified into five types based on the resulting phenotype. The sensitivity to 12 drugs including multityrosine kinase inhibitors was assessed using the MANO method and pazopanib was found to be more effective against cells expressing the COL1A1-PDGFB fusion gene compared with the others. The downstream MAPK/AKT pathway was suppressed at the protein level following pazopanib treatment. The fusion genes were classified into four subgroups by cluster analysis of the gene expression data and gene set enrichment analysis. In summary, the oncogenicity and drug sensitivity of 59 fusion genes were simultaneously evaluated using a high-throughput strategy. Pazopanib was selected as a candidate drug for sarcomas harboring the COL1A1-PDGFB fusion gene. This assessment could be useful as a screening platform and provides a database to evaluate customized therapy for fusion gene-associated sarcomas.

A novel colony-stimulating factor 1 (CSF1) translocation involving human endogenous retroviral element in a tenosynovial giant cell tumor

Tenosynovial giant cell tumors (TSGCTs) are rare tumors arising in tendons or the synoviae of joints and bursae. The localized type is benign while the diffuse type shows expansive growth leading to greater morbidity and is therefore considered locally aggressive. Typical recurrent chromosomal aberrations are found in the majority of TSCGT and the CSF1 gene is frequently involved. In this article, we describe a newly identified gene fusion mediated by an inversion in a case of diffuse TSGCT. Multicolor-fluorescence in situ hybridization (FISH) molecular karyotyping identified a pericentric inversion of chromosome 1 in 7 out of 17 analyzed cells 46,XX,inv(1)(p13.3q24.3) [7]/46,XX [10], and with interphase FISH the involvement the CSF1 locus was detected. After performing transcriptome sequencing analysis for fusion detection, only one out of five fusion gene algorithms detected a fusion involving the CSF1 gene product. The resulting chimera fuses a sequence from a human endogenous retrovirus (HERV) gene to CSF1 Exon 6 on chromosome 1, abrogating the regulatory element of the 3' untranslated region of the CSF1 gene. This new translocation involving Exon 6 of the CSF1 gene fused to 1q24.1, supports the hypothesis that a mutated CSF1 protein is likely to play a vital role in the pathogenesis of TSGCT. The role of the HERV partner identified as a translocation partner, however, remains unclear. Our data add to the complexity of involved translocation partners in TSGCT and point to the potential difficulty of identifying fusion partners in tumor diagnostics using transcriptome sequencing when HERV or other repeat elements are involved.

Targeted therapies for the treatment of soft tissue sarcoma

Soft tissue sarcomas are rare malignant tumors derived from mesenchymal cells that have a high morbidity and mortality related to frequent occurrence of advanced and metastatic disease. Over the past two decades there have been significant advances in the use of targeted therapies for the treatment of soft tissue sarcoma. The ability to study various cellular markers and pathways related to sarcomagenesis has led to the creation and approval of multiple novel therapies. Herein, we describe the current landscape of targeted medications used in the management of advanced or metastatic soft tissue sarcomas, excluding GIST. We distinguish three categories: targeted therapies that have current US Food and Drug Administration (FDA) approval for treatment of soft tissue sarcoma, non-FDA approved targeted therapies, and medications in development for treatment of patients with soft tissue sarcoma.

Best clinical management of tenosynovial giant cell tumour (TGCT): A consensus paper from the community of experts

Tenosynovial giant cell tumour (TGCT) is a rare, locally aggressive, mesenchymal tumor arising from the joints, bursa and tendon sheaths. TGCT comprises a nodular- and a diffuse-type, with the former exhibiting mostly indolent course and the latter a locally aggressive behavior. Although usually not life-threatening, TGCT may cause chronic pain and adversely impact function and quality of life (QoL). CSFR1 inhibitors are effective with benefit on symptoms and QoL but are not available in most countries. The degree of uncertainty in selecting the most appropriate therapy and the lack of guidelines on the clinical management of TGCT make the adoption of new treatments inconsistent across the world, with suboptimal outcomes for patients. A global consensus meeting was organized in June 2022, involving experts from several disciplines and patient representatives from SPAGN to define the best evidence-based practice for the optimal approach to TGCT and generate the recommendations presented herein.

Novel CSF1R-positive tenosynovial giant cell tumor cell lines and their pexidartinib (PLX3397) and sotuletinib (BLZ945)-induced apoptosis

Tenosynovial giant cell tumor (TGCT) is a mesenchymal tumor derived from the synovium of the tendon sheath and joints, most frequently in the large joints. The standard of care for TGCTs is surgical resection. A new targeting approach for treating TGCTs has emerged from studies on the role of the CSF1/CSF1 receptor (CSF1R) in controlling cell survival and proliferation during the pathogenesis of TGCTs. We established four novel cell lines isolated from the primary tumor tissues of patients with TGCTs. The cell lines were designated Si-TGCT-1, Si-TGCT-2, Si-TGCT-3, and Si-TGCT-4, and the TGCT cells were characterized by CSF1R and CD68. These TGCT cells were then checked for cell proliferation using an MTT assay and three-dimensional spheroid. The responses to pexidartinib (PLX3397) and sotuletinib (BLZ945) were evaluated by two-dimensional MTT assays. All cells were positive for α‑smooth muscle actin (α‑SMA), fibroblast activation protein (FAP), CSF1R, and CD68. Except for Si-TGCT-4, all TGCT cells had high CSF1R expressions. The cells exhibited continuous growth as three-dimensional spheroids formed. Treatment with pexidartinib and sotuletinib inhibited TGCT cell growth and induced cell apoptosis correlated with the CSF1R level. Only Si-TGCT-4 cells demonstrated resistance to the drugs. In addition, the BAX/BCL-2 ratio increased in cells treated with pexidartinib and sotuletinib. With the four novel TGCT cell lines, we have an excellent model for further in vitro and in vivo studies.

Expanding the molecular spectrum of tenosynovial giant cell tumors

Background

While great advances in clinical and pathological description of tenosynovial giant cell tumors (TGCT) have been made, TGCT molecular heterogeneity represents an ongoing challenge. The canonical oncogenic fusion CSF1::COL6A3 is not systematically observed, suggesting that other oncogenic mechanisms are involved in tumorigenesis. This study aims to explore by RNA sequencing a retrospective series of tumors diagnosed as TGCT, in order to provide a better description of their molecular landscape and to correlate molecular features with clinical data.

Methods

We analyzed clinicopathological data and performed whole-exome RNA sequencing on 41 TGCT samples.

Results

RNAseq analysis showed significant higher CSF1 and CSF1-R expression than a control panel of 2642 solid tumors. RNA sequencing revealed fusion transcripts in 14 patients including 6 not involving CSF1 and some previously unreported fusions. Unsupervised clustering on the expression profiles issued from this series suggested two distinct subgroups: one composed of various molecular subtypes including CSF1 and FN1 rearranged samples and one composed of four tumors harboring an HMGA2::NCOR2 fusion, suggesting distinct tumor entities. Overall, 15 patients received at least one systemic anti-CSF1R treatment and clinical improvement was observed in 11 patients, including patients from both clusters.

Discussion

This study reported molecular heterogeneity in TGCT, contrasting with the clinical and pathological homogeneity and the ubiquitous high CSF1 and CSF1R expression levels. Whether molecular diversity may impact the efficacy of systemic treatments needs to be further investigated.

Treatment updates on tenosynovial giant cell tumor

PURPOSE OF REVIEW

Diffuse-type tenosynovial giant cell tumor (dt-TGCT) is a benign clonal neoplastic proliferation arising from the synovium. Patients are often symptomatic, require multiple surgical procedures during their lifetime, and have reduced quality of life (QoL). Surgery is the main treatment with relapse rates ranging from 14 to 55%. The treatment strategy for patients with dt-TGCT is evolving. The purpose of this review is to describe current treatment options, and to highlight recent developments in the knowledge of the molecular pathogenesis of dt-TGCT as well as related therapeutic implications.

RECENT FINDINGS

TGCT cells overexpress colony-stimulating factor 1 (CSF1), resulting in recruitment of CSF1 receptor (CSF1R)-bearing macrophages that are polyclonal and make up the bulk of the tumor, has led to clinical trials with CSF1R inhibitors. These inhibitors include small molecules such as pexidatinib, imatinib, nilotinib, DCC-3014 (vimseltinib), and the monoclonal antibody RG7155 (emactuzumab).

SUMMARY

In conclusion, D-TGCT impairs patients' QoL. The evidence that the pathogenetic loop of D-TGCT can be inhibited has changed the therapeutic armamentarium for this condition. Clinical trials of agents that target CSF1R are currently ongoing. All this new evidence should be taken into consideration within multidisciplinary management.

Tenosynovial giant cell tumors (TGCT): molecular biology, drug targets and non-surgical pharmacological approaches

INTRODUCTION

Tenosynovial giant cell tumor (TGCT) is a mono-articular, benign or locally aggressive and often debilitating neoplasm. Systemic therapies are becoming part of the multimodal armamentarium when surgery alone will not confer improvements. Since TGCT is characterized by colony-stimulating factor-1 (CSF1) rearrangements, the most studied molecular pathway is the CSF1 and CSF1 receptor (CSF1R) axis. Inhibiting CSF1-CSF1R interaction often yields considerable radiological and clinical responses; however, adverse events may cause treatment discontinuation because of an unfavorable risk-benefit ratio in benign disease. Only Pexidartinib is approved by the US FDA; however, the European Medicines Agency has not approved it due to uncertainties on the risk-benefit ratio. Thus, there is a need for safer and effective therapies.

AREAS COVERED

Light is shed on disease mechanisms and potential drug targets. The safety and efficacy of different systemic therapies are evaluated.

EXPERT OPINION

The CSF1-CSF1R axis is the principal drug target; however, the effect of CSF1R inhibition on angiogenesis and the role of macrophages, which are essential in the postoperative course, needs further elucidation. Systemic therapies have a promising role in treating mainly diffuse-type, TGCT patients who are not expected to clinically improve from surgery. Future drug development should focus on targeting neoplastic TGCT cells.

Role of colony-stimulating factor 1 in the neoplastic process of tenosynovial giant cell tumor

Tenosynovial giant cell tumors (TGCTs) are rare, locally aggressive, mesenchymal neoplasms, most often arising from the synovium of joints, bursae, or tendon sheaths. Surgical resection is the first-line treatment, but recurrence is common, with resulting impairments in patients' mobility and quality of life. Developing and optimizing the role of systemic pharmacologic therapies in TGCT management requires an understanding of the underlying disease mechanisms. The colony-stimulating factor 1 receptor (CSF1R) has emerged as having an important role in the neoplastic processes underlying TGCT. Lesions appear to contain CSF1-expressing neoplastic cells derived from the synovial lining surrounded by non-neoplastic macrophages that express the CSF1R, with lesion growth stimulated by both autocrine effects causing proliferation of the neoplastic cells themselves and by paracrine effects resulting in recruitment of CSF1 R-bearing macrophages. Other signaling pathways with evidence for involvement in TGCT pathogenesis include programmed death ligand-1, matrix metalloproteinases, and the Casitas B-cell lymphoma family of ubiquitin ligases. While growing understanding of the pathways leading to TGCT has resulted in the development of both regulatory approved and investigational therapies, more detail on underlying disease mechanisms still needs to be elucidated in order to improve the choice of individualized therapies and to enhance treatment outcomes.

Intramuscular Tenosynovial Giant Cell Tumor Harboring a Novel CSF1-CD96 Fusion Transcript

Tenosynovial giant cell tumors typically arise in the synovium of joints, bursae, or tendon sheaths. They may occur in an intra- or extra-articular location and can be divided into localized and diffuse types. The neoplastic nature of the lesion has been supported by a recurrent CSF1 gene rearrangement in a small subset of lesional cells, of which the most common fusion partner is COL6A3. Herein, we report a case of intramuscular localized tenosynovial giant cell tumor harboring a novel CSF1-CD96 fusion transcript, thus expanding the molecular profile of this tumor.

Bilateral giant cell tumor of tendo Achilles: A case series on reconstruction by peroneus brevis - tibialis posterior tendon

Giant cell tumor of tendon sheath usually is localized painless solitary benign swelling, which presents as a firm nodular gradually growing mass. Giant cell tumor is infrequent in the lower limb and its incidence in the tendo Achilles is rare. It is often diagnosed and treated conservatively as tendinitis in the initial stages. The slow growth and limited functional deficit is the reason for its late presentation where excision of the mass leaves a large residual defect, for which reconstruction of the tendo Achilles has to be done by mobilizing different tendons. A case series of bilateral giant cell tumor of tendo Achilles and study the functional outcome of the reconstructed tendo Achilles using peroneus brevis - tibialis posterior tendons - are presented. The outcome of reconstruction using peroneus brevis - tibialis posterior tendon gave satisfactory outcome at the end of one year. LEVEL OF EVIDENCE: Level 4.

Uncommon and peculiar soft tissue sarcomas: Multidisciplinary review and practical recommendations. Spanish Group for Sarcoma research (GEIS -GROUP). Part II

Among all Soft Tissue sarcomas there are some subtypes with low incidence and/or peculiar clinical behaviour, that need to be consider separately. Most of them are orphan diseases, whose biological characteristics imply a clearly different diagnostic and therapeutic approach from other more common sarcoma tumors. We present a brief and updated multidiciplinary review, focused on practical issues, aimed at helping clinicians in decision making. In this second part we review these subtypes: Alveolar Soft Part Sarcoma, Epithelioid Sarcoma, Clear Cell Sarcoma, Desmoplastic Small Round Cell Tumor, Rhabdoid Tumor, Phyllodes Tumor, Tenosynovial Giant Cell Tumors, Myoepithelial Tumor, Perivascular Epithelioid Cell Neoplasms (PEComas), Extraskeletal Myxoid Chondrosarcoma, NTRK-fusions Sarcomas. Most of them present their own radiological and histopathological feautures, that are essential to know in order to achieve early diagnosis. In some of them, molecular diagnosis is mandatory, not only in the diagnosis, but also to plan the treatment. On the other hand, and despite the low incidence, a great scientific research effort has been made to achieve new treatment opportunities for these patients even with approved indications. These include new treatments with targeted therapies and immunotherapy, which today represent possible therapeutic options. It is especially important to be attentive to new and potential avenues of research, and to promote the conduct of specific clinical trials for rare sarcomas.

Establishment and characterization of a novel cell line, NCC-TGCT1-C1, derived from a patient with tenosynovial giant cell tumor

Tenosynovial giant cell tumor (TGCT) is a mesenchymal tumor arising from the synovium of tendon sheath and joints, characterized by translocation t(1;2)(p13;q37). Clinical behaviors of TGCT range from favorable to locally aggressive and further research is required to lead the identification of novel therapeutic avenues for TGCT. Patient-derived cell lines are an indispensable tool for interrogating molecular mechanisms underlying the progression of disease. However, only one TGCT cell line is currently available from cell banks, and a paucity of adequate patient-derived cells hinders basic and translational research. This study aimed to establish a novel cell line of TGCT. To this end, a novel cell line, NCC-TGCT1-C1 was established from the primary tumor tissue of a 40-year-old female patient with TGCT. The cells exhibited translocation t(1;2)(p13;q37), generating COL6A3-CSF1 fusion gene. The cells were maintained as a monolayer culture through more than 30 passages over 12 months. The cells exhibited continuous growth and the ability for spheroid formation and invasion. When used in a high-throughput assay to evaluate the anti-proliferative effects of 164 anticancer drugs, the cells responded strongly to a kinase inhibitor such as gefitinib, and mitoxantrone. Our results indicate that the novel TGCT cell line, designated NCC-TGCT1-C1, was successfully established and could be used to study TGCT development and the effects of anticancer agents.

COL6A3 promotes cellular malignancy of osteosarcoma by activating the PI3K/AKT pathway

OBJECTIVE In this study, we aimed to investigate the role of COL6A3 on cell motility and the PI3K/AKT signaling pathway in osteosarcoma. METHODS The relative expression of COL6A3 was achieved from a GEO dataset in osteosarcoma tissue. siRNA technology was applied to decrease the COL6A3 expression in cells, and cell counting kit-8 (CCK-8) assay and colony formation analysis were used to examine the cell proliferation potential. Knockdown COL6A3 made the proliferation and colony formation abilities worse than the COL6A3 without interference. Likewise, in contrast to the si-con group, cell invasion and migration were inhibited in the si-COL6A3 group. Moreover, the western blot results suggested that the PI3K/AKT signaling pathway was manipulated by measuring the protein expression of the PI3K/AKT pathway-related markers, due to the COL6A3 inhibition. CONCLUSION COL6A3 plays a crucial role in modulating various aspects of the progression of osteosarcoma, which would provide a potentially effective treatment for osteosarcoma.

The Biological Role of the Collagen Alpha-3 (VI) Chain and Its Cleaved C5 Domain Fragment Endotrophin in Cancer

The collagen alpha-3 (VI) chain encoded by the gene COL6A3 is one of the 3 subunits of collagen VI which is a microfibrillar component of the extracellular matrix and is essential for the stable assembly process of collagen VI. The collagen alpha-3 (VI) chain and the cleaved C5 domain fragment, called endotrophin, are highly expressed in a variety of cancers and play a crucial role in cancer progression. The biological functions of endotrophin in tumors can be driven by adipocytes. Studies have demonstrated that endotrophin can directly affect the malignancy of cancer cells through TGF-β-dependent mechanisms, inducing epithelial–mesenchymal transition and fibrosis of the tumor microenvironment. In addition, endotrophin can also recruit macrophages and endothelial cells through chemotaxis to regulate the tumor microenvironment and ultimately promote tumor inflammation and angiogenesis. Furthermore, COL6A3 and endotrophin serve as novel diagnostic and prognostic biomarkers in cancer and contribute to clinical therapeutic applications in the future. In summary, in this review, we discuss the importance of the collagen alpha-3 (VI) chain and endotrophin in cancer progression, the future clinical applications of endotrophin and the remaining challenges in this field.

Long term term follow-up of tyrosine kinase inhibitors treatments in inoperable or relapsing diffuse type tenosynovial giant cell tumors (dTGCT)

RATIONALE

CSF1R tyrosine kinase inhibitors (TKI) and antibodies yield response rates and tumor control in patients with diffuse type tenosynovial giant cell tumors (dTGCT). The long term management of patients with dTGCT treated with TKI is however not known.

PATIENTS AND METHODS

We conducted a retrospective single center study on the 39 patients with advanced and/or inoperable dTGCT referred to the Centre Leon Berard for a medical treatment. The clinical characteristics and treatments of patients who had received at least one line of CSF1R TKI or Ab was collected from the electronic patient records and analyzed, after this study was approved by the Institutional Review Board of the Centre Leon Berard. Statistics were conducted using SPSS 23.0.

RESULTS

Thirty-nine patients received at least one line of TKI among the 101 patients with histologically confirmed dTGCT refered to this center. Imatinib, nilotinib, pexidartinib, emactuzumab were the most frequently used agents. First line treatment was given for a median duration of 7 months. With a median follow-up from the initiation of TKI of 30 months, the progression-free rate at 30 months is 56% for the 39 patients. 15 patients had recurrent disease after first line CSF1R inhibitor: 12 (80%) received a 2nd line treatment for a median duration of 6 months and a median time to progression (TTP) of 12 months. Six patients had afterwards a recurrent disease and 5 (83%) received a 3rd line treatment for a median duration of 5 months and a median TTP of 9 months. Progression-free rate at 30 months was observed in 3 of 12 (25%) after line 2 and 1 of 5 (20%) after line 3. None of the patients refered died with a median follow-up of 67 months.

CONCLUSIONS

CSF1R TKI or Ab provide prolonged tumor control and symptom relief for a majority of patients with inoperable or relapsing dTGCT, in first and subsequent lines. Multiple lines are required for close to 50% of patients with relapsing dTGCT.

Pexidartinib for the treatment of adult patients with symptomatic tenosynovial giant cell tumor: safety and efficacy

INTRODUCTION

Tenosynovial giant cell tumor (TGCT) is a benign clonal neoplastic proliferation arising from the synovium often causing pain, swelling, joint stiffness, and reduced quality of life. The optimal treatment strategy in patients with diffuse-type TGCT (dt-TGCT) is evolving. Surgery is the main treatment, with a high recurrence rate and surgery-related morbidity. Radiotherapy is associated with important side effects. TGCT cells overexpress colony-stimulating factor 1 (CSF1). Pexidartinib (Turalio™) is a selective CSF1 R inhibitor, which was recently approved by the FDA for the treatment of TGCT.

AREAS COVERED

This article reviews the pharmacological properties, clinical efficacy, and safety of pexidartinib.

EXPERT OPINION

Pexidartinib was effective with an acceptable safety profile for advanced TGCT in phase I-III studies. The phase III trial (ENLIVEN) in unresectable TGCT met its primary endpoints of overall response rate. These results led to FDA approval for this TGCT population. Mixed or cholestatic hepatotoxicity was observed in rare cases. For this reason, pexidartinib is currently available only through a Risk Evaluation and Mitigation Strategy (REMS) Program in the USA. TGCT significantly impairs patients' quality of life. The approval of pexidartinib has changed the therapeutic armamentarium for this condition. However, strict monitoring of liver function is warranted.

Current Approaches for Personalized Therapy of Soft Tissue Sarcomas

Soft tissue sarcomas (STS) are a highly heterogeneous group of cancers of mesenchymal origin with diverse morphologies and clinical behaviors. While surgical resection is the standard treatment for primary STS, advanced and metastatic STS patients are not eligible for surgery. Systemic treatments, including standard chemotherapy and newer chemical agents, still play the most relevant role in the management of the disease. Discovery of specific genetic alterations in distinct STS subtypes allowed better understanding of mechanisms driving their pathogenesis and treatment optimization. This review focuses on the available targeted drugs or drug combinations based on genetic aberration involved in STS development including chromosomal translocations, oncogenic mutations, gene amplifications, and their perspectives in STS treatment. Furthermore, in this review, we discuss the possible use of chemotherapy sensitivity and resistance assays (CSRA) for the adjustment of treatment for individual patients. In summary, current trends in personalized management of advanced and metastatic STS are based on combination of both genetic testing and CSRA.

Massively parallel sequencing of tenosynovial giant cell tumors reveals novel CSF1 fusion transcripts and novel somatic CBL mutations

Tenosynovial giant cell tumor (TSGCT) is a rare neoplasm. Although surgical resection is the widely accepted primary treatment for TSGCT, recurrences are frequent, and patients' joint function may be severely compromised. Previous studies reported that CSF1-COL6A3 fusion genes were identified in approximately 30% of TSGCTs. The aim of our study was to comprehensively clarify the genomic abnormalities in TSGCTs. We performed whole exome sequencing in combination with target sequence validation on 34 TSGCT samples. RNA sequencing was also performed on 18 samples. RNA sequencing revealed fusion transcripts involving CSF1, including novel CSF1-VCAM1, CSF1-FN1 and CSF1-CDH1 fusions, in 13/18 (72%) cases. These fusion genes were validated by chromogenic in situ hybridization. All CSF1 fusions resulted in the deletion of CSF1 exon 9, which was previously shown to be an important negative regulator of CSF1 expression. We also found that 12 (35%) of the 34 TSGCT samples harbored CBL missense mutations. All mutations were detected in exons 8 or 9, which encode the linker and RING finger domain. Among these mutations, C404Y, L380P and R420Q were recurrent. CBL-mutated cases showed higher JAK2 expression than wild-type CBL cases (p = 0.013). CSF1 fusion genes and CBL mutations were not mutually exclusive, and both alterations were detected in six of the 18 (33%) tumors. The frequent deletion of CSF1 exon 9 in the fusion transcripts suggested the importance of this event in the etiology of TSGCT. Our results may contribute to the development of new targeted therapies using JAK2 inhibitors for CBL-mutated TSGCT.

Diagnosis of fusion genes using targeted RNA sequencing

Fusion genes are a major cause of cancer. Their rapid and accurate diagnosis can inform clinical action, but current molecular diagnostic assays are restricted in resolution and throughput. Here, we show that targeted RNA sequencing (RNAseq) can overcome these limitations. First, we establish that fusion gene detection with targeted RNAseq is both sensitive and quantitative by optimising laboratory and bioinformatic variables using spike-in standards and cell lines. Next, we analyse a clinical patient cohort and improve the overall fusion gene diagnostic rate from 63% with conventional approaches to 76% with targeted RNAseq while demonstrating high concordance for patient samples with previous diagnoses. Finally, we show that targeted RNAseq offers additional advantages by simultaneously measuring gene expression levels and profiling the immune-receptor repertoire. We anticipate that targeted RNAseq will improve clinical fusion gene detection, and its increasing use will provide a deeper understanding of fusion gene biology.

Rapid and accurate detection of fusion genes is important in cancer diagnostics. Here, the authors demonstrate that targeted RNA sequencing provides fast, sensitive and quantitative gene fusion detection and overcomes the limitations of approaches currently in clinical use.

Malignant Tenosynovial Giant Cell Tumor: The True "Synovial Sarcoma?" A Clinicopathologic, Immunohistochemical, and Molecular Cytogenetic Study of 10 Cases, Supporting Origin from Synoviocytes

We present our experience with ten well-characterized malignant tenosynovial giant cell tumors, including detailed immunohistochemical analysis of all cases and molecular cytogenetic study for CSF1 rearrangement in a subset. Cases occurred in 7 M and 3 F (mean age: 52 years; range: 26-72 years), and involved the ankle/foot (n = 1), finger/toe (n = 3), wrist (n = 1), pelvic region (n = 3), leg (n = 1), and thigh (n = 1). There were eight primary and two secondary malignant tenosynovial giant cell tumors. Histologically, all cases showed definite areas of typical tenosynovial giant cell tumor. The malignant areas varied in appearance. In some cases, isolated malignant-appearing large mononuclear cells with high nuclear grade and mitotic activity were identified within otherwise-typical tenosynovial giant cell tumor, as well as forming larger masses of similar-appearing malignant cells. Occasionally, these nodules of malignant large mononuclear cells showed transition to pleomorphic spindle cell sarcoma, with varying degrees of collagenization and myxoid change. One malignant tenosynovial giant cell tumor was composed of sheets of monotonous large mononuclear cells with high nuclear grade, growing in a hyalinized, osteoid-like matrix, with areas of heterologous osteocartilaginous differentiation. Mitotic activity ranged from 2 to 34 mitoses per 10 HPF (mean 18/10 HPF). Geographic necrosis was observed in four cases. The malignant-appearing large mononuclear cells were consistently positive for clusterin and negative for CD163, CD68, and CD11c. Desmin was positive in a small minority of these cells. Areas in malignant tenosynovial giant cell tumor resembling pleomorphic spindle cell sarcoma or osteo/chondrosarcoma showed loss of clusterin expression. RANKL immunohistochemistry was positive in the large mononuclear cells in eight cases. Two cases showed an unbalanced rearrangement of the CSF1 locus. Follow-up (nine patients; range 0.5-66 months; mean 20 months) showed three patients dead of disease, with three other living patients having lung and lymph node metastases; three patients were disease-free. We conclude that malignant tenosynovial giant cell tumors are highly aggressive sarcomas with significant potential for locally destructive growth, distant metastases, and death from disease. The morphologic and immunohistochemical features of these tumors and the presence of CSF1 rearrangements support origin of malignant tenosynovial giant cell tumor from synoviocytes.

Giant Cell Tumor of Tendon Sheath and Tendinopathy as Early Features of Early Onset Sarcoidosis

Giant cell tumor of tendon sheath (GCTTS) is characterized by diffuse proliferation of synovial-like cells and multinucleated giant cells along tendon sheaths. This benign tumor typically presents in the third to fourth decade of life and is exceeding rare in children. Here we describe a case of a 10-years-old girl with a history of soft tissue swelling involving the third digit of left hand, bilateral wrists and ankles. Pathology of the finger mass revealed abundant multinucleated giant cells consistent with GCTTS. Resection of the tendinous masses from the ankles also showed multinucleated giant cells along with chronic bursitis. She began to show features of polyarticular arthritis by age 7. Due to progression of arthritis, whole exome sequencing was performed and found a de novo heterozygous mutation in NOD2 (p. R334Q). This variant is the most common mutation responsible for early onset sarcoidosis (EOS)/Blau syndrome, an autoinflammatory disease characterized by granulomatous inflammation of joints, skin and eyes. The early onset of symptoms and presence of multinucleated giant cells and granuloma in this case are in keeping with a diagnosis of EOS/Blau syndrome. The patient responded well to treatment with methotrexate and etanercept. This case extends the clinical spectrum of EOS/Blau syndrome, which should be considered for GCTTS and other unusual presentations of tendon inflammation in children, even in the absence of the characteristic triad of arthritis, dermatitis and uveitis.

Clinical characteristics and treatment outcomes in six cases of malignant tenosynovial giant cell tumor: initial experience of molecularly targeted therapy

Background

Although tenosynovial giant cell tumor (TGCT) is classified as a benign tumor, it may undergo malignant transformation and metastasize in extremely rare occasions. High aberrant expression of CSF1 has been implicated in the development of TGCT and recent studies have shown promising activity of several CSF1R inhibitors against benign diffuse-type TGCT; however, little is known about their effects in malignant TGCT.

Case presentation

Information from six consenting patients (3 men, 3 women) with malignant TGCT presenting to Dana-Farber Cancer Institute for initial or subsequent consultation was collected. Median age at initial diagnosis of TGCT was 49.5 years (range 12–55), and median age at diagnosis of malignant TGCT was 50 years (range 34–55). Two patients developed malignant TGCT de novo, while four other cases showed metachronous malignant transformation. All tumors arose in the lower extremities (3 knee, 2 thigh, 1 hip). Five patients underwent surgery for the primary tumors, and four developed local recurrence. All six patients developed lung metastases, and four of five evaluable tumors developed inguinal and pelvic lymph node metastases. All six patients received systemic therapy. Five patients were treated with at least one tyrosine kinase inhibitor with inhibitory activity against CSF1R; however, only one patient showed clinical benefit (SD or PR). Five patients were treated with conventional cytotoxic agents. Doxorubicin-based treatment showed clinical benefit in all four evaluable patients, and gemcitabine/docetaxel showed clinical benefit in two patients. All six patients died of disease after a median of 21.5 months from diagnosis of malignant TGCT.

Conclusions

This study confirms that TGCT may transform into an aggressive malignant tumor. Lymph node and pulmonary metastases are common. Local recurrence rates are exceedingly high. Conventional cytotoxic chemotherapy showed clinical benefit, whereas tyrosine kinase inhibitors against CSF1R showed limited activity. Given its rarity, a prospective registry of malignant TGCT patients is needed to further understand the entity and to develop effective strategies for systemic treatment.

Alternative PDGFD rearrangements in dermatofibrosarcomas protuberans without PDGFB fusions

Dermatofibrosarcoma protuberans is underlined by recurrent collagen type I alpha 1 chain-platelet-derived growth factor B chain (COL1A1-PDGFB) fusions but ~ 4% of typical dermatofibrosarcoma protuberans remain negative for this translocation in routine molecular screening. We investigated a series of 21 cases not associated with the pathognomonic COL1A1-PDGFB fusion on routine fluorescence in situ hybridization (FISH) testing. All cases displayed morphological and clinical features consistent with the diagnosis of dermatofibrosarcoma protuberans. RNA-sequencing analysis was successful in 20 cases. The classical COL1A1-PDGFB fusion was present in 40% of cases (n = 8/20), and subsequently confirmed with a COL1A1 break-apart FISH probe in all but one case (n = 7/8). 55% of cases (n = 11/20) displayed novel PDGFD rearrangements; PDGFD being fused either to the 5' part of COL6A3 (2q37.3) (n = 9/11) or EMILIN2 (18p11) (n = 2/11). All rearrangements led to in-frame fusion transcripts and were confirmed at genomic level by FISH and/or array-comparative genomic hybridization. PDGFD-rearranged dermatofibrosarcoma protuberans presented clinical outcomes similar to typical dermatofibrosarcoma protuberans. Notably, the two EMILIN2-PDGFD cases displayed fibrosarcomatous transformation and homozygous deletions of CDKN2A at genomic level. We report the first recurrent molecular variant of dermatofibrosarcoma protuberans involving PDGFD, which functionally mimic bona fide COL1A1-PDGFB fusions, leading presumably to a similar autocrine loop-stimulating PDGFRB. This study also emphasizes that COL1A1-PDGFB fusions can be cytogenetically cryptic on FISH testing in a subset of cases, thereby representing a diagnostic pitfall that pathologists should be aware of.

Dermatofibrosarcoma protuberans with a novel COL6A3-PDGFD fusion gene and apparent predilection for breast

Dermatofibrosarcoma protuberans is a locally aggressive superficial mesenchymal neoplasm. It typically occurs in adulthood, and has been reported to have a slight male predilection. Tumors have a characteristic histopathologic appearance, including: storiform architecture, infiltrative "honeycomb" growth within subcutaneous adipose tissue, and immunoreactivity for CD34. Virtually all molecularly characterized cases to date have been found to harbor a COL1A1-PDGFB fusion product. Following identification of an index patient with a novel COL6A3-PDGFD fusion gene, we undertook a molecular investigation, using a combination of RNA sequencing and fluorescence in situ hybridization (FISH), to assess the prevalence of PDGFD rearrangement in dermatofibrosarcoma protuberans (N = 63). Three additional patients were found to have balanced PDGFD rearrangements. Interestingly, all 4 tumors arose on the breast of females. As a result, we subsequently examined 16 additional cases of primary breast dermatofibrosarcoma protuberans, identifying 2 additional tumors with PDGFD rearrangement. The morphology and immunophenotype of all 6 cases was analogous to those with the canonical COL1A1-PDGFB fusion; none of the cases showed fibrosarcomatous transformation. This study illustrates that the COL6A3-PDGFD fusion product is rare in dermatofibrosarcoma protuberans, and associated with an apparent predilection for breast. An awareness of this variant is important for pathologists, as it will not be detected using conventional reverse transcription polymerase chain reaction or FISH-based diagnostic assays for dermatofibrosarcoma protuberans.

Silencing of COL1A2, COL6A3, and THBS2 inhibits gastric cancer cell proliferation, migration, and invasion while promoting apoptosis through the PI3k-Akt signaling pathway

This study explores the effect of COL1A2, COL6A3, and THBS2 gene silencing on proliferation, migration, invasion, and apoptosis of gastric cancer cells through the PI3K-Akt signaling pathway. The gastric cancer microarray expression data (GSE19826, GSE79973, and GSE65801) was analyzed. Gastric cancer tissues and corresponding adjacent normal tissues were extracted from patients. Positive expression rate of PI3K, Akt, and p-Akt was measured with immunohistochemistry. Two cell lines, BGC-823 and SGC-7901, were transfected and cells were grouped into blank, negative control, COL1A2-shRNA, COL6A3-shRNA, and THBS2-shRNA groups. Expressions of COL1A2, COL6A3, and THBS2 in gastric cancer cells transfected with corresponding silencing sequences were evaluated by RT-qPCR and Western blot. MTT assay, Transwell, and cell scratch tests were conducted to evaluate cell proliferation, invasion, and migration capacity, respectively. Flow cytometry was used to evaluate cell cycle distribution and apoptosis. The positive expression of PI3K, Akt, and p-Akt was higher in gastric cancer tissues compared with adjacent normal tissues, and the mRNA expression of COL1A2, COL6A3, and THBS2 was increased in gastric cancer tissues. Akt, p-Akt, and PI3K expression drastically decreased in cells transfected with COL1A2, COL6A3, and THBS2 silencing sequences. Cells transfected with COL1A2, COL6A3, and THBS2 silencing sequences exhibited promoted apoptosis but inhibited proliferation, migration, and invasion. This study demonstrates that COL1A2, COL6A3, and THBS2 gene silencing inhibits gastric cancer cell proliferation, migration, and invasion while promoting apoptosis through the PI3K-Akt signaling pathway.

Diagnostic utility of histone H3.3 G34W, G34R, and G34V mutant-specific antibodies for giant cell tumors of bone

Giant cell tumors of bone (GCTBs) are characterized by mononuclear stromal cells and osteoclast-like giant cells; up to 95% have H3F3A gene mutation. The RANKL inhibitor denosumab, when used for the treatment of GCTB, leads to histological changes such as new bone formation and giant cell depletion. Here we assessed the diagnostic utility of immunohistochemical staining with the antibodies against histone H3.3 G34W, G34R and G34V mutant proteins for GCTB and other histologically similar bone and joint lesions. H3.3 G34W, G34R and G34V expressions were detected in mononuclear stromal cells in 47/51 (92%), 1/51 (2%) and 3/51 (6%) cases of primary GCTBs, respectively, in a mutually exclusive manner. All recurrent/metastatic GCTBs (n=14), post-denosumab GCTBs (n=8) and secondary malignant GCTBs (n=2) were positive for H3.3 G34W. The immunohistochemical results were essentially correlated with the H3F3A genotype determined by mutation analysis. In post-denosumab GCTBs, H3.3 G34W expression was seen in immature bone-forming cells. H3.3 G34W, G34R and G34V were negative in 121/122 cases of non-GCTB, including chondroblastoma, osteosarcoma, primary aneurysmal bone cyst and other giant cell-rich lesions. The exception was a single case of undifferentiated high-grade pleomorphic sarcoma that was positive for H3.3 G34W, suggesting the possibility of sarcomatous overgrowth of primary malignant GCTB. Therefore, H3.3 G34W/R/V mutant-specific antibodies are useful surrogate markers for the H3F3A genotype and helpful for the diagnosis of GCTB and its variants. The expression of H3.3 G34W mutant protein in post-denosumab GCTB suggests that neoplastic stromal cells may play a role in new bone formation.

Structural, spectroscopic and molecular docking studies on 2-amino-3-chloro-5-trifluoromethyl pyridine: A potential bioactive agent

The most stable, optimized structure of the 2-amino-3-chloro-5-trifluoromethyl pyridine (ACTP) molecule was predicted by the density functional theory calculations using the B3LYP method with cc-pVQZ basis set. Antitumor activity of the ACTP molecule was evaluated by molecular docking analysis. The structural parameters and vibrational wavenumbers were calculated for the optimized molecular structure. The experimental and theoretical vibrational wavenumbers were assigned and compared. Ultraviolet-visible spectrum was simulated and validated experimentally. The molecular electrostatic potential surface was simulated. Frontier molecular orbitals and related molecular properties were computed and further density of states spectrum was simulated. The natural bond orbital analysis was also performed to confirm the bioactivity of the ACTP molecule. The molecular docking analysis reveals the better inhibitory nature of the ACTP molecule against the colony-stimulating factor 1 (CSF1) gene which causes tenosynovial giant-cell tumor. Hence, the ACTP molecule can act as a potential inhibitor against tenosynovial giant-cell tumor.

Coexisting sarcoidal granulomatous inflammation and diffuse tenosynovial giant cell tumor of the knee after a total knee replacement: a case report

Sarcoidosis is a systemic inflammatory disorder characterized by non-caseating granulomas, predominantly involving lung, mediastinal lymph nodes and other organs. Synovium involvement is infrequent, and as far as we know, involvement of a periprosthetic membrane has not been reported in the English literature. Intra-articular diffuse tenosynovial giant cell tumor ("conventional diffuse pigmented villonodular synovitis") is an uncommon, locally aggressive neoplasm with few previous case reports in which it arose in periprosthetic tissues after knee arthroplasty. We describe a unique case of an intraarticular mass next to a total knee prosthesis implanted 6 years ago in a patient with a history of pulmonary sarcoidosis. Clinically, this 67-year-old gentleman presented with progressive left knee pain, effusion and marked instability. MRI showed a large complex effusion with synovial thickening in the supra patella recess and the medial and lateral gutters. In addition, a large multilobulated mass with mixed low and high signal intensity was present in the posterior joint space, extending into the popliteal area. A two-stage operation was performed. Histologically, the mass from the posterior joint space showed characteristic features of diffuse tenosynovial giant cell tumor, while the synovium from the anterior compartment demonstrated sarcoidal granulomatous inflammation. Orthopaedic wear debris was found within the giant cells of these sarcoidal granulomata. The histologic features are different from those "usual" macrophage reactions to the particles of debris. In this article, we also included two optional links (highlighted in blue in the figures) to digital whole slide image (WSI), which allow the readers to navigate the entire microscope slides.

Refinements in Sarcoma Classification in the Current 2013 World Health Organization Classification of Tumours of Soft Tissue and Bone

The fourth edition of the World Health Organization (WHO) Classification of Tumours of Soft Tissue and Bone was published in February 2013. The 2013 WHO volume provides an updated classification scheme and reproducible diagnostic criteria, which are based on recent clinicopathologic studies and genetic and molecular data that facilitated refined definition of established tumor types, recognition of novel entities, and the development of novel diagnostic markers. This article reviews updates and changes in the classification of bone and soft tissue tumors from the 2002 volume.

Polyarticular extension of pigmented villonodular synovitis to contiguous joints via pigmented villonodular tenosynovitis

Pigmented villonodular synovitis is an uncommon benign neoplastic process that affects synovial-lined joints, bursae and tendon sheaths. We describe polyarticular extension of pigmented villonodular synovitis across joints secondary to pigmented villonodular tenosynovitis. Given that treatment is required to prevent progressive destruction of the involved joint, tendon or bursa, radiologists must be vigilant for diffuse polyarticular or extrasynovial involvement to optimize patient care and initiate appropriate therapy.

Multi-lineage differentiation and angiogenesis potentials of pigmented villonodular synovitis derived mesenchymal stem cells--pathological implication

Pigmented villonodular synovitis (PVNS) is a benign tissue proliferation characterized by its hyper-vascularity within the lesion. The true etiology and cell source of this disease entity still remain unclear. Mesenchymal stem cells (MSCs) exist in various tissues of human body. However, it has not been clarified whether MSCs could be isolated from tissue of PVNS. Here, we isolated MSCs from PVNS (PVNS-SCs), and by comparing to the MSCs from normal synovium (Syn-SCs) of the same individual, we investigated whether PVNS-SCs differed in the capacity for multi-differentiation and inducing angiogenesis. We first demonstrated that PVNS-SCs existed in the lesion of PVNS of three individuals. Moreover, we showed PVNS-SCs had better osteogenic differentiation potential than Syn-SCs, whereas Syn-SCs had better capacity for adipogenic and chondrogenic differentiation. By genome-wide analysis of gene expression profile using a complementary DNA microarray and comparing to Syn-SCs, we identified in PVNS-SCs a distinct gene expression profile characterized by up-regulation of genes involved in angiogenesis. In vitro and in vivo studies further confirmed that PVNS-SCs had better capacities for promoting angiogenesis. In summary, the identification of PVNS-SCs in PVNS tissue and their distinct angiogenic potential may help elucidate the underlying etiology of this disease.

Selected Lesions Featuring Giant Cells

Many neoplasms of the soft tissues feature giant cells, but this article covers entities in which giant cells are a striking feature. Specifically, we consider tenosynovial giant cell tumor (localized and diffuse types; giant cell tumor of tendon sheath, and pigmented villonodular tenosynovitis), reticulohistiocytoma, juvenile xanthogranuloma, giant cell fibroblastoma (a variant form of dermatofibrosarcoma protuberans), giant cell angiofibroma (which is essentially a giant cell-rich form of solitary fibrous tumor), and phosphaturic mesenchymal tumor.

Expression of colony-stimulating factor 1 is associated with occurrence of osteochondral change in pigmented villonodular synovitis

Pigmented villonodular synovitis (PVNS) is a benign, translocation-derived neoplasm. Because of its high local recurrence rate after surgery and occurrence of osteochondral destruction, a novel therapeutic target is required. The present study aimed to evaluate the significance of protein expression possibly associated with the pathogenesis during the clinical course of PVNS. In 40 cases of PVNS, positivity of colony-stimulated factor 1 (CSF1), its receptor (CSF1R), and receptor activator of nuclear factor kappa-B ligand (RANKL) were immunohistochemically determined. The relationship between the positivity and clinical outcomes was investigated. High positivity of CSF1 staining intensity was associated with an increased incidence of osteochondral lesions (bone erosion and osteoarthritis) (p = 0.009), but not with the rate of local recurrence. Positivity of CSF1R and RANKL staining was not associated with any clinical variables. The number of giant cells was not correlated with positivity of any of the three proteins, or with the clinical outcome. Focusing on knee cases, CSF1 positivity was also associated with the incidence of osteochondal change (p = 0.02). CSF1R positivity was high in cases which had local recurrence, but not significantly so (p = 0.129). Determination of CSF1 and CSF1R expression may be useful as a prognosticator of the clinical course and/or outcomes of PVNS.

WHO classification of soft tissue tumours: an update based on the 2013 (4th) edition

The fourth edition of the World Health Organization (WHO) Classification of Tumours of Soft Tissue and Bone was published in February 2013, and serves to provide an updated classification scheme and reproducible diagnostic criteria for pathologists. Given the relative rarity of soft tissue tumours and the rapid rate of immunohistochemical and genetic/molecular developments (not infrequently facilitating recognition of new tumour entities), this updated text edited by a consensus group is important for both practising pathologists and oncologists. The 2013 WHO classification includes several changes in soft tissue tumour classification, including several new entities (e.g., pseudomyogenic haemangioendothelioma, haemosiderotic fibrolipomatous tumour, and acral fibromyxoma), three newly included sections for gastrointestinal stromal tumours, nerve sheath tumours, and undifferentiated/unclassified soft tissue tumours, respectively, various 'reclassified' tumours, and a plethora of new genetic and molecular data for established tumour types that facilitate better definition and are useful as diagnostic tools. This article briefly outlines these updates based on the 2013 WHO classification of soft tissue tumours.

Soft tissue perineurioma of the foot with 10q24 rearrangements: unique MRI features with histopathologic correlation

Perineurioma is an uncommon benign peripheral nerve sheath tumor with advanced perineurial differentiation. Two distinct subtypes are recognized: intraneural and soft tissue. We herein present a unique case of soft tissue perineurioma in the right foot of a 43-year-old man. Radiographs showed a non-specific soft tissue mass. On computed tomography scan, the mass was iso- to slightly hypodense relative to muscle. On T1- and T2-weighted images, the mass exhibited iso- to slightly low signal intensity relative to muscle with foci of high signal intensity. Slight contrast enhancement was noted on enhanced T1-weighted images with fat suppression. A marginal excision of the tumor was performed and histopathologic examination confirmed the diagnosis of soft tissue perineurioma. The clinicopathologic, radiologic, and cytogenetic findings are described, and the relevant literature is reviewed.

Novel CSF1-S100A10 fusion gene and CSF1 transcript identified by RNA sequencing in tenosynovial giant cell tumors

RNA-sequencing was performed on three tenosynovial giant cell tumors (TSGCT) in an attempt to elicit more information on the mechanisms of CSF1 expression in this tumor type. A novel CSF1-S100A10 fusion gene was found in a TSGCT that carried the translocation t(1;1)(q21;p11) as the sole karyotypic abnormality. In this fusion gene, the part of CSF1 coding for the CSF1 protein (exons 1-8 in sequences with accession nos. NM_000757 and NM_172212) is fused to the 3'-part of S100A10. Since the stop codon TAG of CSF1 is present in it, the CSF1-S100A10 fusion gene's predominant consequence seems to be the replacement of the 3'-untranslated region (UTR) of CSF1 (exon 9; nt 2092-4234 in sequence with accession no. NM_000757 or nt 2092-2772 in NM_172212) by the 3'-end of S100A10 (exon 3; nt 641-1055 in sequence with accession no. NM_002966). In the other two TSGCT, a novel CSF1 transcript was detected, the same in both tumors. Similar to the occurrence in the CSF1-S100A10 fusion gene, the novel CSF1 transcript 3'-UTR is replaced by a new exon located ~48 kb downstream of CSF1 and 11 kb upstream of AHCYL1. Although only 3 TSGCT were available for study, the finding in all of them of a novel CSF1-S100A10 fusion gene or CSF1 transcript indicates the existence of a common pathogenetic theme in this tumor type: the replacement of the 3'-UTR of CSF1 with other sequences.