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Background: Pigmented villonodular synovitis is a rare yet locally invasive disorder impacting synovial tissues. This case report delineates the atypical manifestation of pigmented villonodular synovitis in the talonavicular joint, detailing its diagnostic complexity and successful management. Case presentation: A 56-year-old Iranian patient with a 4-year history of chronic ankle pain, initially diagnosed with degenerative joint disease post-trauma based on imaging, underwent talonavicular fusion surgery. An unexpected pigmented villonodular synovitis mass was encountered during the procedure. Subsequent interventions encompassed tumor resection, talonavicular joint fusion, and allograft bone grafting. Despite the initial intervention, persistent pain and nonunion necessitated a secondary procedure, involving joint surface curettage and autograft bone grafting. At the 12-month follow-up, the patient remained pain-free without tumor recurrence. Conclusion: This case report highlights the significance of considering pigmented villonodular synovitis as a crucial differential diagnosis in chronic ankle pain, even when there is evidence of degenerative joint disease and a history of trauma. Magnetic resonance imaging serves a crucial role in accurate diagnosis. Treatment necessitates precise tumor removal, appropriate bone grafting techniques and secure fixation. Level of evidence: IV. [ABSTRACT FROM AUTHOR]

This article discusses a case of sudden knee joint swelling in a 61-year-old male with a nodular lesion of Hoffa's fat pad. The patient presented with pain, swelling, and reduced range of motion in the left knee joint. An MRI revealed a nodular lesion in the fat pad of Hoffa, fluid in the suprapatellar bursa and knee joint, and edema in the biceps femoris muscle. The lesion was surgically resected and diagnosed as local pigmented villonodular synovitis (PVNS) of the knee. PVNS is a rare neoplastic synovial disease characterized by joint effusions, bone erosion, and synovial hyperplasia. It primarily affects young adults and is most commonly found in the knee and hip joints. The diagnosis of PVNS can be suggested on MRI, and excision and tissue sampling are required for a definitive diagnosis. PVNS should be differentiated from other synovial lesions with hemosiderin deposition. [Extracted from the article]

Key Clinical Message: In this case report, total knee arthroplasty was performed in a patient with pigmented villonodular synovitis. During surgery, severe black discoloration of the articular cartilage and menisci was observed in the patient. According to literatures, this is the first case report of severe articular cartilage pigmentation in a patient with pigmented villonodular synovitis. [ABSTRACT FROM AUTHOR]

We report on a 40-year-old male with a 9-month-long history of snapping of his right hip caused by a previously undescribed etiology of internal extra-articular snapping hip, namely due to a localized tenosynovial giant cell tumor. Both dynamic ultrasound evaluation and MRI proved to be crucial in the diagnosis of this rare entity. Auto-provocation of the snapping showed an anterior hip mass moving posteriorly to the psoas tendon which elucidated the pain and clicking sensation. Subsequent MRI demonstrated a peripheral low-intensity rim due to hemosiderin deposition around the synovial mass which is indicative for pigmented villonodular tenosynovitis. Treatment consisted of arthroscopic shaver burr resection. Immediately postoperatively, the snapping sensation could not be provoked anymore by the patient. The purpose of reporting on this case report is to emphasize several successive learning points. First, dynamic ultrasound aids in diagnosis and differentiation of the types of snapping hip. Second, specific MRI features are suggestive of tenosynovial giant cell tumor, recognizing these traits may prevent delayed diagnosis and subsequent aggravated clinical course. Third, localized pigmented villonodular tenosynovitis around the hip may present as an internal extra-articular snapping hip and is of consideration in the differential diagnosis of recurrent snapping hip. [ABSTRACT FROM AUTHOR]

Introduction: Early synovectomy is considered as the main treatment of pigmented villonodular synovitis (PVNS) of the hip in young patients with preserved cartilage. The purpose of the study is to evaluate outcomes of arthroscopic management for PVNS of the hip. Methods: Patients who underwent primary hip arthroscopy for the treatment of histology-confirmed PVNS by the senior author between January 2012 and December 2016 were retrospectively reviewed. We excluded patients who had less than 1-year follow-up or had undergone primary surgeries with other surgeons and then received revision hip arthroscopic procedures by the senior author. The recurrence of PVNS and postoperative condition of affected hip were assessed by follow-up magnetic resonance imaging (MRI). Patient-reported outcomes of modified Harris hip score (mHHS) and 12-item International Hip Outcome Tool (iHOT-12) were collected at latest follow-up. Results: Nine patients (2 males, 7 females) with a mean age of 24.3 ± 11.2 years (range 14–44 years) were included in this study. Localized PVNS was observed in four patients, and diffuse PVNS was observed in five patients. No patient presented with advanced osteochondral destruction. Five patients received single adjuvant radiosynoviorthesis. No patient had evidence of recurrence based on follow-up MRI. Patient-reported outcomes were obtained in eight patients at mean 55.8 ± 26.1 months (range 24–84 months) after the index surgery. The mean mHHS was 94.6 ± 4.9 (range 84.7–100) and the mean iHOT-12 was 93.3 ± 20.2 (range 50–120). No patient needed secondary surgery during the follow-up period. Conclusion: Arthroscopic subtotal synovectomy can offer favorable short to mid-term outcomes in the treatment of hip PVNS in case of no advanced osteochondral damage at presentation. [ABSTRACT FROM AUTHOR]

Diffuse-type tenosynovial giant cell tumour (D-TGCT) is a non-malignant but locally aggressive tumour driven by overexpression of colony-stimulating factor-1 (CSF1). CSF1R inhibitors are potential therapeutic strategies for patients not amenable to surgery. We report here the long-term outcome of nilotinib in patients with advanced D-TGCT treated within a phase II prospective international study (ClinicalTrials.gov: NCT01261429). Patients were enrolled between December 2010–September 2012 at 11 cancer centres. Eligible patients had histologically confirmed D-TGCT, not amenable to surgery. Patients received nilotinib until evidence of progression, toxicity or a maximum of one year. Long-term data were retrospectively collected after the completion of the phase II trial. Patients with nilotinib treatment ≥12 weeks and follow-up ≥12 months were included for long-term analysis. Forty-eight of 56 enrolled patients were included. Median treatment duration was 11 months; 31 (65%) patients completed the treatment protocol. After 102 months of follow-up (median; range 12–129), 25 patients (52%) had progression. The median progression-free survival (PFS) was 77 months. The five-year PFS rate was 53%. Fifteen patients (n = 15/46; 33%) experienced clinical worsening after 11 months (median). Twenty-seven patients (58%) received additional treatment, after which eleven patients (n = 11/27; 41%) had a second relapse. Nine patients required a subsequent treatment, primarily other CSF1R inhibitors (n = 6/9; 67%). No unfavourable long-term effects were observed. This long-term analysis of nilotinib for advanced D-TGCT showed that about half of the patients had progression and underwent additional treatment after 8.5 years follow-up. Contrarily, several patients had ongoing disease control after limited treatment duration, demonstrating the mixed effect of nilotinib. • TGCT is mainly driven by CSF1 overexpression. • Nilotinib was the CSF1R inhibitor investigated in a phase II clinical trial in TGCT. • This is the first study describing the long-term efficacy of nilotinib on D-TGCT. • Nilotinib showed mixed long-term efficacy regarding progression-free survival. • The current role of nilotinib in TGCT is questionable. [ABSTRACT FROM AUTHOR]

Background: Diffuse pigmented villonodular synovitis (DPVNS) is a challenging tumor-like disorder that mainly occurs in the anterior aspect of the knee joint. The growth may sometimes extend to the posterior knee joint. Surgical excision is the mainstream treatment for DPVNS, and the posterior approach of tumor excision is adopted when the dominant tumor shows posterior extension. However, the optimal surgical approach over the posterior knee remains unknown. Methods: Patients with DPVNS of the knee joint who received the posterior approach of synovectomy from 1995 to 2019 were retrospectively reviewed to describe the modified separate posterior (SP) approaches, and evaluate the treatment outcomes in a case series of DPVNS knees. The results of the SP approach was also compared with those of traditional direct posterior (DP) approach. Postoperative functional outcomes were evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) standardized questionnaire and clinician-completed Musculoskeletal Tumor Society (MSTS) functional rating system at outpatient department. Results: A total of 20 DPVNS knees were included. Thirteen patients who received SP approaches were included in the SP group, while seven patients who received the DP approach were included in the DP group. The median follow-up times were 5.7 years (IQR, 2-8.8) in the SP group and 3 years (IQR, 2-5.3) in the DP group. Both groups showed satisfactory safety. The SP group presented higher postoperative mean WOMAC (91.23 ± 7.20) and mean MSTS (24.23 ± 2.68) than the DP group (mean WOMAC: 76.00 ± 16.57; mean MSTS: 22.43 ± 4.69). The Wilcoxon signed-rank test was use to compare preoperative and postoperative range of motion (ROM) for each group. The significant difference in SP group (p = 0.004) was found while p = 0.131 in DP group. Conclusions: The SP approach provides an effective approach with satisfactory outcomes for the surgical treatment of DPVNS knees. [ABSTRACT FROM AUTHOR]

Tenosynovial giant cell tumor-diffuse type (diffuse TSGCT) is a benign but locally aggressive proliferative disorder of the synovium. Treatment is usually surgical, although in cases of extensive disease complete synovectomy is not possible and local recurrence rates are high. Pexidartinib (trade name Turalio®), a colony-stimulating factor-1 (CSF-1) inhibitor, was shown in a recent phase III trial to effectively treat diffuse TSGCT and is FDA approved for the treatment of adult patients with symptomatic diffuse TSGCT associated with severe morbidity or functional limitations and not amenable to improvement with surgery. Pexidartinib is available only through a restricted program under a risk evaluation and mitigation strategy (REMS) because of the risk of hepatotoxicity. Magnetic resonance imaging (MRI) is the preferred imaging modality for the diagnosis and surveillance of TSGCT. Here we present three patients with diffuse TSGCT of the knee who underwent multiple MRIs over several years while on pexidartinib. We describe the disease burden and signal characteristics on MRI and correlate with the response reported in the patients' medical records. Given that the use of pexidartinib and other CSF inhibitors is likely to increase, musculoskeletal radiologists should be aware of this novel non-operative treatment and the MRI appearance of diffuse TSGCT during therapy. [ABSTRACT FROM AUTHOR]

Background: Diffuse pigmented villonodular synovitis (DPVNS) is a challenging tumor-like disorder that mainly occurs in the anterior aspect of the knee joint. The growth may sometimes extend to the posterior knee joint. Surgical excision is the mainstream treatment for DPVNS, and the posterior approach of tumor excision is adopted when the dominant tumor shows posterior extension. However, the optimal surgical approach over the posterior knee remains unknown.Methods: Patients with DPVNS of the knee joint who received the posterior approach of synovectomy from 1995 to 2019 were retrospectively reviewed to describe the modified separate posterior (SP) approaches, and evaluate the treatment outcomes in a case series of DPVNS knees. The results of the SP approach was also compared with those of traditional direct posterior (DP) approach. Postoperative functional outcomes were evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) standardized questionnaire and clinician-completed Musculoskeletal Tumor Society (MSTS) functional rating system at outpatient department.Results: A total of 20 DPVNS knees were included. Thirteen patients who received SP approaches were included in the SP group, while seven patients who received the DP approach were included in the DP group. The median follow-up times were 5.7 years (IQR, 2-8.8) in the SP group and 3 years (IQR, 2-5.3) in the DP group. Both groups showed satisfactory safety. The SP group presented higher postoperative mean WOMAC (91.23 ± 7.20) and mean MSTS (24.23 ± 2.68) than the DP group (mean WOMAC: 76.00 ± 16.57; mean MSTS: 22.43 ± 4.69). The Wilcoxon signed-rank test was use to compare preoperative and postoperative range of motion (ROM) for each group. The significant difference in SP group (p = 0.004) was found while p = 0.131 in DP group.Conclusions: The SP approach provides an effective approach with satisfactory outcomes for the surgical treatment of DPVNS knees. [ABSTRACT FROM AUTHOR]

Tenosynovial giant cell tumor (TGCT) is a neoplasm of the joint synovium that can have severe impacts on joint mobility, function, and quality of life. Traditionally, treatment modalities included partial or complete surgical synovectomy, radiotherapy (typically as an adjunct to surgery), and watchful monitoring (no medical or surgical intervention). However, these approaches have been met with varying degrees of success and high recurrence rates, as well as onerous complications and clinical sequelae. Pexidartinib, a colony-stimulating factor 1 receptor (CSF1R) inhibitor, presents a promising molecular approach that targets a neoplastic driver of TGCT. While the introduction of pexidartinib allows clinicians to avoid the significant morbidity associated with traditional treatment options, there are also defined risks associated with pexidartinib treatment. Therefore, patient selection is critical in optimizing treatment modalities in TGCT. The purpose of this literature review is to identify the TGCT patient population that would derive maximal benefit with minimal risk from pexidartinib, and to determine the specific indications and contraindications for selecting pexidartinib over other therapeutic approaches. Specifically, this paper compares the efficacy and safety profile of pexidartinib across clinical and preclinical studies to that of surgery, radiotherapy, and watchful monitoring. Rates of improvement in joint mobility, pain, and recurrence-free survival across studies of pexidartinib have been encouraging. The most common adverse events are mild (hypopigmentation of the hair) or reversible (transient aminotransferase elevation). Severe or permanent adverse events (notably cholestatic hepatotoxicity) are rare. While the optimal treatment strategy remains highly dependent on a patient's clinical circumstances and treatment goals, pexidartinib has surfaced as a promising therapeutic in cases where the morbidity of surgery or radiotherapy outweighs the benefits. [ABSTRACT FROM AUTHOR]

Cases: We used the modified Stoppa approach in a 17-year-old man with a retained bullet in his acetabular fossa. The acetabular hole was used to irrigate the hip joint. We also used this approach in a 29-year-old woman with right hip pain and limping to remove an isolated tenosynovial giant cell tumor ("localized pigmented villonodular synovitis") in the acetabular fossa expanding through the acetabulum. Discussion: We believe that this approach should become more familiar because it offers a simple alternative for treating acetabular pathologies mainly involving the acetabular fossa, sparing patients the hazards of capsulotomy, trochanteric osteotomy, dislocation, and traction and fluid pressure in hip arthroscopy. [ABSTRACT FROM AUTHOR]

Tenosynovial giant cell tumor-diffuse type (diffuse TSGCT) is a benign but locally aggressive proliferative disorder of the synovium. Treatment is usually surgical, although in cases of extensive disease complete synovectomy is not possible and local recurrence rates are high. Pexidartinib (trade name Turalio®), a colony-stimulating factor-1 (CSF-1) inhibitor, was shown in a recent phase III trial to effectively treat diffuse TSGCT and is FDA approved for the treatment of adult patients with symptomatic diffuse TSGCT associated with severe morbidity or functional limitations and not amenable to improvement with surgery. Pexidartinib is available only through a restricted program under a risk evaluation and mitigation strategy (REMS) because of the risk of hepatotoxicity. Magnetic resonance imaging (MRI) is the preferred imaging modality for the diagnosis and surveillance of TSGCT. Here we present three patients with diffuse TSGCT of the knee who underwent multiple MRIs over several years while on pexidartinib. We describe the disease burden and signal characteristics on MRI and correlate with the response reported in the patients' medical records. Given that the use of pexidartinib and other CSF inhibitors is likely to increase, musculoskeletal radiologists should be aware of this novel non-operative treatment and the MRI appearance of diffuse TSGCT during therapy. [ABSTRACT FROM AUTHOR]

Pigmented villonodular synovitis (PVNS) is a benign lesion that usually occurs in tendon sheaths, in burses or in the large joints synovia of the extremities. The pathogenesis of PVNS is still not clear, recently defined as a benign clonal neoplastic proliferation. PVNS is often asymptomatic and it is incidentally diagnosed in the majority of cases; given its local aggressiveness and the high rate of local recurrences it requires wide excision to be successfully treated. In rare cases PVNS can have malignant features sometimes with metastatic diffusion. The malignant form is often associated to the presence of colony-stimulating factor 1 (CSF1) gene mutation. In this report we present a brief literature review and the first case of recurrent hip PVNS with vertebral metastases, associated to an unusual genetic mutation. [ABSTRACT FROM AUTHOR]

The tumor-permissive and immunosuppressive characteristics of tumor-associated macrophages (TAM) have fueled interest in therapeutically targeting these cells. In this context, the colony-stimulating factor 1 (CSF1)/ colony-stimulating factor 1 receptor (CSF1R) axis has gained the most attention, and various approaches targeting either the ligands or the receptor are currently in clinical development. Emerging data on the tolerability of CSF1/ CSF1R-targeting agents suggest a favorable safety profile, making them attractive combination partners for both standard treatment modalities and immunotherapeutic agents. The specificity of these agents and their potent blocking activity has been substantiated by impressive response rates in diffuse-type tenosynovial giant cell tumors, a benign connective tissue disorder driven by CSF1 in an autocrine fashion. In the malignant disease setting, data on the clinical activity of immunotherapy combinations with CSF1/CSF1R-targeting agents are pending. As our knowledge of macrophage biology expands, it becomes apparent that the complex phenotypic and functional properties of macrophages are heavily influenced by a continuum of survival, differentiation, recruitment, and polarization signals within their specific tissue environment. Thus, the role of macrophages in regulating tumorigenesis and the impact of depleting and/or reprogramming TAM as therapeutic approaches for cancer patients may vary greatly depending on organ-specific characteristics of these cells. We review the currently available clinical safety and efficacy data with CSF1/CSF1R-targeting agents and provide a comprehensive overview of ongoing clinical studies. Furthermore, we discuss the local tissue macrophage and tumor-type specificities and their potential impact on CSF1/CSF1R-targeting treatment strategies for the future. [ABSTRACT FROM AUTHOR]

Radiosynoviorthesis (RSO) is an attractive alternative to surgical synovectomy for controlling symptoms of rheumatoid arthritis and many other chronic proliferative joint diseases. The procedure is not widely used in our country because of the non-availability of suitable radionuclides and radiopharmaceuticals. The production of rhenium-188 (188Re) from 188W/188Re generator and by labelling it with particles of appropriate size, has a promise to offer. We labelled 188Re with tin colloid and analyzed its biodistribution and clinical efficacy after injecting it to a patient with recurrent pigmented villonodular synovitis. Gamma camera imaging performed after 1, 24 and 48 hrs showed no leakage of the radiopharmaceutical from the injected joint. The clinical outcome of this study was also excellent, which suggests that 188Re labelled tin colloid is a potentially effective radiopharmaceutical for recurrent PVNS and can be used for other chronic inflammatory joint diseases. [ABSTRACT FROM AUTHOR]

Synovial and chondromatous lesions can extend dorsally, intermetatarsally and deep into the vault of the longitudinal and transverse plantar arches of the foot. The lesions may prove difficult to excise even with combined approaches. Two cases where a transmetatarsal approach by excision of the base of the third metatarsal enabled successful complete excision of the lesions are presented. Level of Evidence: Level V, expert opinion. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to determine the characteristic computed tomography (CT) findings of pigmented villonodular synovitis (PVNS) of the temporomandibular joint (TMJ). Study design: Eight subjects with PVNS were examined with both pre and post contrast CT scans. All lesions were histopathologically confirmed through surgery. CT appearances of the lesions were reviewed. Results: Among the eight subjects, 8 (100%) demonstrated soft tissue mass and enhancement after contrast administration, 6 (75%) appeared as all or focal areas of noncontrast hyperdensity, 6 (75%) had widening of the joint spaces. Bony erosion of the mandibular condyles and articular surfaces were found in 7 (87.5%) and 6 (75%) subjects, respectively. Conclusions: Based on the CT findings, PVNS of the TMJ is characterized by hyperdensity soft tissue mass and further increase in density after contrast administration, bony destruction of the mandibular condyles and skull base, and intracranial extension. [ABSTRACT FROM AUTHOR]

Purpose: We report on a group of patients with tumours in the Hoffa's fat pad (HFP), their clinical presentation, histological type and treatment, including two synovial sarcomas with their clinical follow-up, which have not been described previously in the literature. Methods: We performed a retrospective review of our prospectively collected database of 25 cases of HFP tumours with at least six months follow-up. Results: The gender, age at presentation (over and under 16 years of age), clinical features, history of trauma, treatment chosen, and complications were recorded. The mean age of the patients was 32 years (three to 47). Six patients were under 16 years old. Pain was the most common symptom, present in 92 % ( n = 23/25). The final diagnoses included 23 (92 %) benign tumours and two (8 %) malignant tumours. The most common benign tumour was pigmented villonodular synovitis (PVNS) (48 % n = 12). The two malignant tumours were synovial sarcomas and both presented in patients under 16 years old. Conclusions: Hoffa's fat pad tumours are an uncommon and rarely diagnosed group of lesions that can be misinterpreted as any knee pathology. Although the majority of HFP tumours are benign, malignant tumours should be considered in the differential diagnosis for the paediatric population. [ABSTRACT FROM AUTHOR]

Pigmented villonodular synovitis (PVNS) is a rare benign proliferative disorder that results in villous hyperplasia and nodule formation in the synovium, tendon sheath and bursa. That most commonly affects the knee and the hip joint in adult. PVNS of the hand, the wrist, the shoulder and the elbow is rare and that of the elbow in children is particularly rarer. An eight-year-old boy had his left elbow pain and a lesion like benign bone tumor in the left fossa olecrani on plain x-ray. During the operation, abnormal synovial hyperplasia in his left elbow joint led us to diagnose PVNS. Therefore, open curettage of the lesion and radical synovectomy was performed. The specimen of the synovectomized tissue revealed PVNS. The left elbow pain subsided after the operation and the child restored a full range of motion of his left elbow. We reported this rare case of PVNS in a child's elbow joint mimicking the bone tumor together with a review of the literature. [ABSTRACT FROM AUTHOR]

Pigmented villonodular synovitis (PVNS) is a rare disease of the synovial membrane. Its relationship to unicompartmental arthroplasty is unknown and it has never been reported as a complication of this procedure. Retrospective review of two cases who presented with this rare condition after Oxford unicompartmental arthroplasty (Biomet, UK). We present their cases and discuss the difficulties we faced in their management. These cases are remarkably similar in their presentation. The diagnosis was confirmed histologically in both cases. We mainly focus on the diagnostic difficulties and our treatment strategies in both cases. We also review the current literature on this unusual disease. [ABSTRACT FROM AUTHOR]

Abstract: Protein expression of osteopontin (OPN), osteoprotegerin (OPG), bone sialoprotein (BSP), osteocalcin (OC), RANKL and PTHrP was determined by use of immunohistochemical analysis on tissue arrays (48 cases of PVNS, 20 cases of active (a-RA), non-active rheumatoid arthritis (na-RA), and osteoarthritis (OA)). Additionally, gene expression was analysed using complimentary DNA (cDNA) microarrays. All PVNS cases showed a higher level of both protein and gene expression of RANKL, OPN and BSP in comparison with OA cases. Expression of OPG was not significantly different in PVNS compared to OA. The RANKL/OPG expression ratio was significantly higher in PVNS than in OA. High expressions level of proteins involved in bone degradation in PVNS may promote an intra-osseous propagation of the lesion. This evidence suggests that PVNS might respond to treatment using specific inhibitors of RANKL, OPN and BSP. [Copyright &y& Elsevier]

Objective: Although it is a rare condition, pigmented villonodular synovitis (PVNS) may involve temporomandibular joint (TMJ). The purpose of this study was to describe magnetic resonance (MR) findings of PVNS of the TMJ. Methods and material: Between April 1992 and August 2000, four patients (two men and two women, 22–58-year-old) who had histologically proven diagnoses of PVNS in their TMJ were found in our institution. Their MR findings were reviewed retrospectively, and were correlated with pathologic findings. Results: In all four patients, MR images invariably showed profound hypointensity on both T1- and T2-weighted sequences. This finding was seen diffusely and homogeneously throughout the lesion, and was considered to be due to paramagnetic effect attributed to heavy hemosiderin pigmentation, which was revealed by histopathological examination. MR images also showed aggressive nature of the lesions with adjacent skull base destruction and intracranial extension in two of them. Conclusion: As is the case in the other anatomic site, PVNS of the TMJ can be confidently diagnosed on MR imaging on the basis of the presence of hemosiderin. MR imaging also plays a pivotal role in surgical planning by precise and detailed localization of the lesion. [Copyright &y& Elsevier]

Background: Tenosynovial giant cell tumors (TGCTs) or giant cell tumors of tendon sheath are neoplasms that arise in the synovium. They can be categorized as nodular (localized) or diffuse type (D-TGCT). Historically, surgery has been the mainstay of therapy, but diffuse type disease recurs at a high rate and treatment often requires increasingly morbid procedures. Elucidation of the importance of the colony-stimulating factor (CSF1)/CSF1 receptor (CSF1R) pathway in the pathogenesis of this disease has created significant interest in targeting this pathway as a novel TGCT treatment approach. Pexidartinib, a selective tyrosine kinase inhibitor against CSF1R, showed an 83% disease control rate (52% with partial response and 31% with stable disease) in a recent phase 1 study of patients with TGCT. Case presentation: We present an illustrative example of a TGCT patient who would have required a morbid operation who derived considerable clinical benefit from pexidartinib treatment. Her tumor volume decreased by 48% after 4 months of treatment, and 55 months after starting treatment the patient exhibits continued disease stability with minimal clinical symptoms, and significant improvement in functional status. Conclusions: This case illustrates the effectiveness of systemic therapy in controlling a disease associated with high surgical morbidity. This approach may be especially useful in the treatment of extra-articular disease which often invades neurovascular bundles; as the effectiveness in metastatic disease is still unknown. In the future, systemic treatment for TGCT may be appropriate for the neoadjuvant setting to decrease disease burden prior to surgery with the aim of decreasing recurrence rates. However, properly designed prospective studies will need to be carried out to answer these questions. [ABSTRACT FROM AUTHOR]