Tenosynovial giant cell tumor, or TGCT, is a neoplasm arising from the synovial lining of joints, bursae, or tendon sheaths. Under the 2020 World Health Organization Classification of Soft Tissue and Bone Tumours, the disease is divided by growth pattern into localized and diffuse types. The diffuse variant, historically known as pigmented villonodular synovitis, is a locally aggressive lesion marked by extensive synovial proliferation, nodular growth, and a strong tendency to recur. It most often strikes the knee, but also appears in the finger, ankle, and shoulder. Hip involvement is uncommon, and that rarity is precisely what makes it so dangerous diagnostically: when a deep, inaccessible joint begins to erode bone, the list of possible culprits is long and includes some far more alarming possibilities.

The patient’s story began one week before admission, when he experienced acute chills and high fever and received three days of empirical intravenous cefuroxime at a local hospital, with partial improvement. Then came the hip pain — acute, severe, worst at night, disturbing his sleep, and worsened by movement. Rest and repositioning did not help. On examination he was afebrile at 36.4°C, with marked tenderness over the right hip, pain provoked by internal rotation, adduction, and flexion, and mildly restricted range of motion. There was no redness, warmth, or swelling, no trauma, no weight loss, and no evening fevers. The distal neurovascular examination was unremarkable. In short, nothing about the physical presentation clearly separated infection from tumor.

Imaging told a more revealing story, though not a definitive one. Magnetic resonance imaging of both hips demonstrated abnormal intra-articular synovial tissue in the right hip, with mild bilateral joint effusion that was more pronounced on the right. The lesion, measuring approximately 27 by 35 by 25 millimeters, showed heterogeneous low-to-intermediate signal intensity on T1-weighted images, heterogeneous signal on T2-weighted images, and heterogeneous enhancement after contrast administration — a signal profile characteristic of TGCT, reflecting variable proportions of fibrous tissue, lipid-laden macrophages, fluid, and hemosiderin deposition. The adjacent anterior acetabular column appeared thinned, and mild swelling of the right obturator externus muscle was noted. Computed tomography then showed joint effusion, cystic low-density intra-articular lesions, and clear thinning and erosion of the anterior and inferomedial acetabular wall. Notably, the plain radiograph showed no definite abnormality, underscoring why advanced imaging is essential when plain films fail.

Laboratory testing deepened the ambiguity rather than resolving it. The white blood cell count was 6.46 × 10⁹/L with 68.4% neutrophils, C-reactive protein was elevated at 34.20 mg/L, the erythrocyte sedimentation rate was 25 mm/h, and procalcitonin measured 0.268 ng/mL — a pattern suggestive of low-grade inflammation but far from conclusive. Serum alkaline phosphatase and tumor markers were normal. Whole-body bone scintigraphy showed increased tracer uptake in both hips, sacroiliac joints, and shoulders, which clinicians judged most consistent with degenerative change. With a recent febrile illness, equivocal inflammatory markers, and a destructive-appearing acetabular lesion, the preoperative differential diagnosis spanned infectious or inflammatory synovitis, synovial chondromatosis, and other aggressive synovial or osseous lesions. Because neither imaging nor laboratory work could deliver a verdict, the team proceeded to surgical exploration after multidisciplinary discussion.

What surgeons found inside the joint settled the immediate uncertainty about the lesion’s nature while illustrating why preoperative diagnosis is so difficult. Intraoperative inspection revealed abundant yellowish joint fluid and diffuse proliferation of synovium-like tissue throughout the right hip, with irregular nodular lesions along the anteromedial and inferomedial acetabular wall. The team performed complete excision of the identified intra-articular lesions and involved synovial tissue, curetted the eroded inferomedial acetabular wall, treated it with alcohol ablation, and reconstructed the localized bone defect with an autologous iliac bone graft. Estimated blood loss was approximately 150 milliliters. Although the lesion contained nodular components measuring up to roughly 1.5 by 3.0 centimeters, it was classified as diffuse-type TGCT because of the widespread intra-articular synovial involvement, the acetabular erosion, and the absence of a solitary encapsulated mass.

Histopathologic examination provided the gold-standard confirmation. Microscopy showed proliferative synovium-like tissue with focal cyst wall-like structures lined by flattened to cuboidal cells, a stroma containing proliferative fibrous tissue, histiocytes, prominent congested vessels, diffuse chronic inflammatory cells, scattered neutrophils, and focal coagulative necrosis. Scattered and clustered foamy histiocytes and variable numbers of osteoclast-like multinucleated giant cells were present, along with hemosiderin granules within the cytoplasm of mononuclear cells and histiocytes — the pigment that gave the old disease its name. Immunohistochemistry showed strong CD68 positivity in the multinucleated giant cells and a subset of mononuclear cells, focal S-100 expression, and a Ki-67 labeling index of approximately 5% to 10%, compatible with low proliferative activity. Focal coagulative necrosis was interpreted as a secondary degenerative or ischemic change, and no cytologic atypia, atypical mitotic activity, or sarcomatous overgrowth was identified. Joint-fluid cultures were negative for bacterial and fungal growth, though the authors caution that prior cefuroxime exposure may have reduced culture sensitivity, so infection could never be excluded on microbiologic grounds alone.

The molecular backdrop of this tumor is one of the more fascinating chapters in modern soft-tissue oncology. TGCT is associated with overexpression of colony-stimulating factor 1, or CSF1, which recruits macrophages to the lesion through what researchers call the landscape effect — a minority population of neoplastic cells orchestrating a massive influx of reactive, non-neoplastic immune cells that constitute most of the tumor’s bulk. This mechanism also underpins CSF1/CSF1R-targeted therapies, which are reserved for selected patients with residual, recurrent, or incompletely resectable disease. In this case, however, gross excision and synovectomy were achieved without postoperative radiotherapy or systemic antitumor therapy, with management transitioning instead to clinical and imaging surveillance.

The recovery course was largely favorable, punctuated by one unrelated complication. The patient experienced marked pain relief immediately after surgery, but on postoperative day three he developed fever, mild cough, and fatigue. Chest CT revealed bilateral patchy opacities, pulmonary infection was diagnosed, and intravenous cefuroxime with supportive care normalized his temperature and resolved his systemic symptoms. Follow-up imaging told a reassuring story: CT on the first postoperative day showed satisfactory filling of the acetabular defect by the bone graft, and at two months the graft maintained its position with osseous incorporation and healing. At the two-week mark the incision was well healed and hip motion had improved beyond preoperative levels. By six months, the patient reported sustained pain improvement and had returned to independent daily activities and work, although mild limitation of right hip motion persisted.

The case, reported in Cancer Reports, carries an educational message that resonates well beyond a single patient. Because the hip joint is deeply situated and its capsule has limited capacity to accommodate proliferative synovium, osseous erosion is a recognized feature of hip D-TGCT — yet a destructive-appearing acetabular lesion inevitably raises concern for septic arthritis, inflammatory synovitis, synovial chondromatosis, or a more aggressive neoplasm. The authors emphasize that MRI remains the preferred modality for mapping the extent of synovial disease, while CT more clearly delineates the osseous erosion relevant to operative planning, making the two techniques complementary rather than interchangeable. Ultimately, imaging alone could not reliably distinguish this tumor from infectious or aggressive etiologies; definitive diagnosis depended on integrating the clinical course, intraoperative observations, and characteristic histopathologic features. The authors frame the report primarily as an educational account of diagnostic evaluation and multidisciplinary management rather than evidence of durable local control, noting that the follow-up period remains short and that recurrence is a recognized concern given the complex anatomy of the hip. Longer surveillance will be needed to assess recurrence, joint function, and treatment durability. The broader lesson stands: diffuse-type tenosynovial giant cell tumor deserves a place on the differential diagnosis of any unexplained erosive intra-articular hip lesion, even when the clinical context screams infection.

Subject of Research: Diffuse-type tenosynovial giant cell tumor of the hip with acetabular bone involvement diagnosed by radiologic-pathologic correlation.

Article Title: Diffuse‐Type Tenosynovial Giant Cell Tumor of the Hip With Acetabular Bone Involvement: A Case Report With Radiologic‐Pathologic Correlation

Article References: Quanbing, W., Huanhuan, X., Xing, Z., Tao, Y., Jun, Z., Lei, Z., Kai, L., Lei, L., Feng, A., & Wei, Y. (2026). Diffuse‐Type Tenosynovial Giant Cell Tumor of the Hip With Acetabular Bone Involvement: A Case Report With Radiologic‐Pathologic Correlation. Cancer Reports, 9(9), Article e70696. https://doi.org/10.1002/cnr2.70696

Image Credits: AI Generated

DOI: 10.1002/cnr2.70696

Keywords: tenosynovial giant cell tumor, diffuse-type TGCT, hip, acetabular erosion, MRI, CT, synovectomy, histopathology, CSF1, case report, orthopedic oncology, diagnostic imaging

Soft tissue sarcomas are a rare and notoriously heterogeneous family of malignancies arising from the body’s mesenchymal tissues—skeletal muscle, fat, fibrous sheaths, blood vessels, and peripheral nerves—collectively accounting for roughly one percent of cancers in adults. Their surgical management is unforgiving. These tumors tend to grow by compressing neighboring structures and sending microscopic extensions along fascial planes, so curative surgery demands wide excision with a cuff of healthy tissue, ideally while preserving the limb’s function. Radiotherapy is added when the risk of local recurrence is high, and the timing of that radiation has become one of the field’s central strategic questions. Delivered before surgery—a strategy known as neoadjuvant radiotherapy—the treatment operates on an intact, well-oxygenated tumor whose full anatomical extent can still be visualized, permitting smaller and more precisely contoured radiation fields than are possible once the surgical bed has been disturbed. Preoperative radiation can also render tumor cells less viable, theoretically reducing the risk of seeding cancer cells during resection, and may shrink bulky lesions enough to convert an amputation into a limb-sparing operation. The trade-offs are real, since wound-healing complications loom larger, and success hinges on disciplined coordination between radiation oncologists and surgeons.

To understand why some physicians embrace this sequence and others hesitate, the researchers turned to the knowledge–attitude–practice framework, a classic construct in health services research that treats clinical behavior as the end product of what clinicians know and what they believe. Between November and December 2023, the team administered an investigator-designed, self-administered questionnaire to specialists recruited from multiple Beijing hospitals through purposive sampling, a technique that deliberately targets respondents with direct experience of the problem under study. The instrument captured baseline characteristics, knowledge, attitudes, and practices concerning neoadjuvant therapy, together with measures of the doctor–patient relationship and the difficulties clinicians perceive in their interactions with patients. Internet Protocol controls were used during questionnaire distribution to prevent duplicate submissions, and the internal consistency of the instrument was verified using Cronbach’s alpha. The study received ethical approval from the review committee of Beijing Jishuitan Hospital and was conducted in accordance with the Declaration of Helsinki, with written informed consent obtained from every participant.

After screening out problematic questionnaires, the analysis settled on 467 valid responses from specialists with a mean age of 42.20 years—an experienced, mid-career cohort that forms the backbone of China’s sarcoma services. Respondents reported a mean doctor–patient relationship score of 22.61, with a standard deviation of 5.62, quantifying the relational climate in which treatment conversations unfold. When the team stratified knowledge, attitude, and practice scores across demographic characteristics, statistically significant differences emerged by department affiliation and by the frequency with which specialists consulted sarcoma patients, with P values below 0.05. In practical terms, a physician’s institutional home and daily caseload—whether one practices within a dedicated bone and soft tissue tumor service or a general orthopedic department, and whether sarcoma patients arrive weekly or only occasionally—leave measurable fingerprints on what doctors know, how they feel, and what they do.

The raw numbers told a strikingly consistent story. Knowledge scores averaged 15.52, with a standard deviation of 2.68, on a scale running from 0 to 18—roughly 86 percent of the theoretical maximum. Attitudes, measured on a possible range of 8 to 40, averaged 34.01, plus or minus 2.87, and practices, on a range of 8 to 30, averaged 26.19, plus or minus 2.99, both again approaching the upper limits of their scales. Taken together, the profile depicts a specialist community that is well informed about neoadjuvant radiotherapy, views it favorably, and reports acting on that conviction in daily clinical work. For a treatment whose adoption has lagged unevenly across health systems worldwide, the documented enthusiasm among Chinese sarcoma specialists is notable, and it provides a rare quantitative baseline for a subspecialty in which practice patterns have been difficult to measure at scale.

The study’s most consequential finding, however, lies beneath the averages. Pairwise analyses showed that knowledge, attitudes, and practices rose and fell together, with positive correlations significant at P < 0.001. To dissect the architecture of those associations, the researchers deployed structural equation modeling, a statistical framework that combines confirmatory factor analysis with simultaneous regression pathways, allowing investigators to test whether one construct directly influences another while estimating indirect routes through intermediate variables. The fitted model, evaluated with conventional goodness-of-fit indices including the root mean square error of approximation and the standardized root mean square residual, delivered an unambiguous verdict: knowledge exerted a direct positive effect on attitude, with a standardized coefficient of 0.526 at P = 0.007, and attitude exerted a direct positive effect on practice, with a coefficient of 0.516 at P = 0.005. Knowledge, by contrast, showed no statistically significant direct effect on practice. Its influence traveled entirely through attitude, producing a significant indirect effect of 0.271 at P = 0.002. In plain terms, knowing about preoperative radiotherapy does not by itself move a clinician’s hands; it must first move a clinician’s mind.

The survey’s attention to the doctor–patient relationship adds a distinctly human dimension to the statistics. Using the ten-item Difficult Doctor–Patient Relationship Questionnaire, the investigators captured how strained or smooth clinicians find their encounters with patients—a critical variable in oncology, where choosing radiation before surgery requires patients to accept a probabilistic benefit whose costs, in the form of early wound complications, arrive sooner than its rewards. Communication in high-volume orthopedic oncology clinics is shaped by time pressure, uneven health literacy, and the anxiety of families confronting a diagnosis most have never heard of before the day it is delivered. By embedding this relational measure within the same instrument, the authors positioned the clinical encounter itself as part of the machinery through which knowledge becomes practice, acknowledging that even the most confident specialist recommendation must survive a negotiation with a frightened patient weighing surgery, radiation, and the future use of a limb.

The findings land amid a broader recalibration of sarcoma care. Clinical guidance from bodies such as the National Comprehensive Cancer Network and the Chinese Society of Clinical Oncology frames the role of perioperative radiotherapy in high-risk soft tissue sarcoma, and the field is watching the rise of total neoadjuvant therapy—an emerging paradigm in which radiation and systemic treatment are delivered together before surgery, a strategy already reshaping management in other tumor types and now under active scrutiny in sarcoma. Against that backdrop, the variation detected across departments and consultation frequencies reads as a warning about the concentration of expertise: where sarcoma patients are rare, so is the accumulated judgment that converts guidelines into confident action. The authors argue that the response must be systemic—optimizing policies and healthcare services, and directing continuing education not merely at transmitting facts but at cultivating the convictions those facts are meant to produce, because a model in which knowledge acts only through attitude will stall wherever attitude is left unaddressed.

As with any cross-sectional survey, the study captures a single moment and cannot prove the causal direction its elegant statistical fit implies. Purposive sampling concentrated on Beijing hospitals, so the results describe an urban, tertiary-care elite and may not extend to physicians in smaller cities and regional hospitals, where a large share of Chinese patients first seek care. Self-reported practices can diverge from audited clinical behavior, and the questionnaire, while internally consistent, was investigator-designed rather than borrowed wholesale from prior validated instruments. The authors declared no funding and no competing interests, and the paper is being shared early in citable form ahead of final production. These caveats temper, but do not dismantle, the central result, which rests on a large sample, transparent measurement, and a modeling approach whose assumptions can be inspected and retested in other populations.

For patients, the study’s message is easiest to state in anatomical terms: a limb spared, a margin clean, a recurrence avoided—each is more likely when the physicians orchestrating care both understand preoperative radiotherapy and believe in it. What this research demonstrates is that the believing part is not automatic. It is built, measurably, on a foundation of knowledge, and it serves as the engine that converts learning into action. The Beijing team’s quantified pathway from knowledge through attitude to practice offers health systems a map with marked intervention points: strengthen knowledge, and attitudes follow; nurture attitudes, and practice follows. If the goal is care that keeps pace with the best available evidence, the study suggests, medical systems must invest in shaping conviction as deliberately as they invest in disseminating information—an insight that likely extends well beyond sarcoma radiation, to every corner of medicine where guidelines and real-world behavior diverge.