Radiomics of multi-parametric MRI for the prediction of lung metastasis in soft-tissue sarcoma: a feasibility study.

PURPOSE: To investigate the value of multi-parametric MRI-based radiomics for preoperative prediction of lung metastases from soft tissue sarcoma (STS). METHODS: In total, 122 patients with clinicopathologically confirmed STS who underwent pretreatment T1-weighted contrast-enhanced (T1-CE) and T2-weighted fat-suppressed (T2FS) MRI scans were enrolled between Jul. 2017 and Mar. 2021. Radiomics signatures were established by calculating and selecting radiomics features from the two sequences. Clinical independent predictors were evaluated by statistical analysis. The radiomics nomogram was constructed from margin and radiomics features by multivariable logistic regression. Finally, the study used receiver operating characteristic (ROC) and calibration curves to evaluate performance of radiomics models. Decision curve analyses (DCA) were performed to evaluate clinical usefulness of the models. RESULTS: The margin was considered as an independent predictor (p < 0.05). A total of 4 MRI features were selected and used to develop the radiomics signature. By incorporating the margin and radiomics signature, the developed nomogram showed the best prediction performance in the training (AUCs, margin vs. radiomics signature vs. nomogram, 0.609 vs. 0.909 vs. 0.910) and validation (AUCs, margin vs. radiomics signature vs. nomogram, 0.666 vs. 0.841 vs. 0.894) cohorts. DCA indicated potential usefulness of the nomogram model. CONCLUSIONS: This feasibility study evaluated predictive values of multi-parametric MRI for the prediction of lung metastasis, and proposed a nomogram model to potentially facilitate the individualized treatment decision-making for STSs.

Growth Rate and Outcomes in Locally Recurrent Extremity and Truncal Soft Tissue Sarcoma.

Importance: Improved prognostic tools are needed for patients with locally recurrent extremity or truncal soft tissue sarcoma (STS). Objective: To examine the association between average local recurrence (LR) growth rate and outcomes following resection of locally recurrent extremity or truncal STS. Design, Setting, and Participants: This retrospective cohort study used a prospectively maintained database from a single high-volume tertiary sarcoma referral center in the US to identify patients 16 years of age or older who underwent repeat resection of a locally recurrent extremity or truncal STS between July 1, 1982, and December 31, 2021. Patients with atypical lipomatous tumors, desmoid tumors, dermatofibrosarcoma protuberans, angiosarcomas, and prior or synchronous distant recurrence were excluded. Data were analyzed from November 1, 2022, to June 17, 2024. Exposure: Average LR growth rate, defined as the sum of recurrent tumor maximal diameters divided by the disease-free interval after index operation. Main Outcomes and Measures: The primary outcomes were cumulative incidences of disease-specific death (DSD), with death from other causes as a competing risk, and second LR, with death from any cause as a competing risk. Results: The study cohort included 253 patients (median [IQR] age, 64 [51-73] years; 140 [55.3%] male). The 5-year cumulative incidence of DSD after repeat resection was 29%. Multivariable analysis indicated that LR growth rate (hazard ratio [HR], 1.12 [95% CI, 1.08-1.18]; P < .001), younger age (HR, 0.98 [95% CI, 0.97-0.99]; P = .002), R1 or R2 margins (HR, 1.71 [95% CI, 1.03-2.84]; P = .04), high LR grade (HR, 2.90 [95% CI, 1.17-7.20]; P = .02), and multifocality (HR, 2.92 [95% CI, 1.70-5.00]; P < .001) were independently associated with higher incidence of DSD. Using the minimum P value method, the optimal cutoff for growth rate was found to be 0.68 cm/mo. Patients with values above this cutoff had higher 5-year incidences of DSD following repeat resection (63% vs 19%; permutation test P < .001) and higher amputation rates (19% vs 7%; P = .008). Only R1 margins were independently associated with higher incidence of second LR (HR, 1.81 [95% CI, 1.19-2.78]; P = .006). Conclusions and Relevance: In this cohort study of patients undergoing resection of a locally recurrent extremity or truncal STS, LR growth rate was independently associated with DSD. These findings suggest that patients with growth rates higher than 0.68 cm/mo who undergo LR resection may have high disease-specific mortality and amputation rates and should be considered for perioperative systemic therapy.

Atypical Presentation of Tenosynovial Giant Cell Tumor on the Hallucal Flexor Tendon Sheath: A Case Report.

Tenosynovial giant cell tumor (TGCT) is a rare type of neoplasm that may be locally aggressive but is most often benign and can be divided into two subtypes: localized and diffuse. It tends to develop in the joints, bursae, and tendon sheaths primarily in the digits of the hand and less commonly in the forefoot. This soft-tissue mass has many possible differential diagnoses, including lipoma, ganglion cyst, plantar fibroma, and various sarcomas; surgical excision is usually indicated to reach a definitive diagnosis and rule out malignancy. We report a rare case of a 30-year-old woman with atypical plantar hallucal pain and a palpable mass on the plantar lateral aspect of the left hallux. Surgical excision and histopathologic evaluation confirmed a TGCT of the left hallucal flexor tendon sheath. Although it bears clinical resemblance to several other soft-tissue masses, TGCT has numerous pathognomonic features evident with advanced imaging and histologic analysis that help the physician obtain an accurate diagnosis and proceed with appropriate treatment.

Large Nodular Fasciitis of the Shoulder Presenting as Soft Tissue Sarcoma: A Case Report.

CASE: This case report describes a patient who presented with clinical and radiographic features of a soft tissue sarcoma of the shoulder. Despite having a painless and relatively large mass, a biopsy and resection revealed nodular fasciitis (NF). CONCLUSION: This is an unusual case of a painless 10 cm mass that histopathologically was diagnosed as NF in the upper extremity with proximity to the axillary nerve and posterior humeral circumflex vessels. The USP6 rearrangement was helpful in confirming the diagnosis. Careful clinical, radiographic, and pathologic correlation is necessary in diagnosing these relatively rare tumors. In cases where there are discordant findings, molecular markers can be very helpful.

Doxorubicin-Trabectedin with Trabectedin Maintenance in Leiomyosarcoma.

BACKGROUND: The addition of trabectedin to doxorubicin, followed by trabectedin maintenance, may have superior efficacy to doxorubicin alone as first-line treatment in patients with advanced leiomyosarcoma. METHODS: We conducted a phase 3 trial involving patients with metastatic or unresectable leiomyosarcoma who had not received chemotherapy previously. Patients were randomly assigned to receive either single-agent doxorubicin (six cycles) or doxorubicin plus trabectedin (six cycles), with continued trabectedin as maintenance therapy in patients in the doxorubicin-trabectedin group who did not have disease progression. Surgery to resect residual disease was allowed in each group after six cycles of therapy. Analyses of progression-free survival (primary end point) and overall survival (secondary end point) were adjusted for two stratification factors: tumor origin site (uterine vs. soft tissue) and disease stage (locally advanced vs. metastatic). The primary end-point results were reported previously. RESULTS: A total of 150 patients underwent randomization. At a median follow-up of 55 months (interquartile range, 49 to 63), a total of 107 patients had died (47 in the doxorubicin-trabectedin group and 60 in the doxorubicin group). The median overall survival was longer in the doxorubicin-trabectedin group (33 months; 95% confidence interval [CI], 26 to 48) than in the doxorubicin group (24 months; 95% CI, 19 to 31); the adjusted hazard ratio for death was 0.65 (95% CI, 0.44 to 0.95). In a finding consistent with earlier reports, progression-free survival was longer in the doxorubicin-trabectedin group (12 months; 95% CI, 10 to 16) than in the doxorubicin group (6 months; 95% CI, 4 to 7); the adjusted hazard ratio for progression or death was 0.37 (95% CI, 0.26 to 0.53). The incidence of adverse events and the percentage of patients with dose reductions were higher with doxorubicin plus trabectedin than with doxorubicin alone. CONCLUSIONS: Combination therapy with doxorubicin and trabectedin induction, followed by trabectedin maintenance, was associated with improved overall survival and progression-free survival, as compared with doxorubicin alone, among patients with metastatic or surgically unresectable uterine or soft-tissue leiomyosarcoma. (Funded by PharmaMar and others; LMS04 ClinicalTrials.gov number, NCT02997358.).

Soft Tissue Fine-Needle Aspiration: Current and Future Impact on Patient Care.

Soft tissue neoplasms pose many diagnostic challenges on fine-needle aspiration (FNA), owing largely to their rarity, large number of entities, and histologic diversity. Advances in ancillary testing now allow detection of the characteristic immunophenotypes and molecular alterations for many neoplasms and include reliable surrogate immunohistochemical markers for underlying molecular events that are highly efficient in small biopsies. A morphology-based framework is recommended to guide appropriate differentials and judicious selection of ancillary tests for small biopsies. The accurate diagnosis of soft tissue tumors is crucial for patient management and prognostication, with many potential implications in this era of precision medicine.

Superficial Atypical Lipomatous Tumor With Pleomorphic Features: Case Report and Discussion of the Literature.

ABSTRACT: Among liposarcomas, well-differentiated liposarcoma and dedifferentiated liposarcoma are the most common. The majority of these tumors are found in deep retroperitoneum or extremities. When found outside the retroperitoneum, these adipose-derived tumors are known as atypical lipomatous tumors (ALT). Superficial ALT are particularly rare; thus, little is known about their clinical presentation, genomic status, and management. Here, we present the case of a 54-year-old man with an intermittently bothersome, slowly growing mass on his left upper back for over 2 years, which was incidentally diagnosed as ALT. This patient's ALT, however, showed a profound degree of pleomorphism with MDM2 and control centromere 12 (CEP12) coamplification and negative CD34 and S100 and RB1 expression, unlike most other ALT described in the literature. This case report details the diagnostic workup and histopathological findings for adipose tumors and summarizes the different subtypes, including atypical spindle cell/pleomorphic lipomatous tumor, pleomorphic liposarcoma, and spindle cell/pleomorphic lipoma, with brief discussion on management.

Comparisons of magnetic resonance imaging, histopathological and Ki-67 labeling index findings in a single myxofibrosarcoma: a case report.

BACKGROUND: Myxofibrosarcoma is a myxoid soft tissue sarcoma showing T2 high intensity on magnetic resonance imaging. However, myxofibrosarcoma is a heterogeneous sarcoma with both myxoid and cellular portions. Magnetic resonance imaging findings were obtained MRI findings for comparison with histological and Ki-67 immunohistochemical features, in different portions of one myxofibrosarcoma. CASE PRESENTATION: Magnetic resonance imaging observations were compared with gross pathological and microscopic findings of a myxofibrosarcoma from a 50-year-old Japanese female. The Ki-67 labeling indices of different portions of the tumor, that is, the myxoid, cellular, and histologically confirmed infiltrative margin portions (pathological tail sign), were compared. The T2 low intensity area was more cellular than the T2 high intensity area, while the cellular portion had a significantly higher Ki-67 index than the myxoid portion (p = 0.0313). The portions with the pathological tail sign had a significantly higher Ki-67 labeling index than those without this sign (p = 0.0313). CONCLUSIONS: More cellular portions of a myxofibrosarcoma correspond to more areas of the tumor showing aggressive features. Furthermore, our data also support the hypothesis of high aggressiveness being associated with the pathological tail sign in myxofibrosarcoma. To our knowledge, this is the first case report to describe comparisons among the imaging findings, histological features, and Ki-67 immunohistochemistry results for different portions of one myxofibrosarcoma.

Progress in histology specific treatments in soft tissue sarcoma.

INTRODUCTION: Soft tissue sarcomas (STS) represent a heterogenous group of rare tumors, primarily treated with surgery. Preoperative radiotherapy is often recommended for extremity high-risk STS. Neoadjuvant chemotherapy, typically based on doxorubicin with ifosfamide, has shown efficacy in limbs and trunk wall STS. Second-line chemotherapy, commonly utilized in the metastatic setting, is mostly histology-driven. Molecular targeted agents are used across various histologies, and although the use of immunotherapy in STS is still in its early stages, there is increasing interest in exploring its potential. AREAS COVERED: This article involved an extensive recent search on PubMed. It explored the current treatment landscape for localized and metastatic STS, focusing on the combined use of radiotherapy and chemotherapy for both extremity and retroperitoneal tumors, and with a particular emphasis on the most innovative histopathology driven therapeutic approaches. Additionally, ongoing clinical trials identified via clinicaltrials.gov are included. EXPERT OPINION: Recently there have been advancements in the treatment of STS, largely driven by the outcomes of clinical trials. However further research is imperative to comprehend the effect of chemotherapy, targeted therapy and immunotherapy in various STS, as well as to identify biomarkers able to predict which patients are most likely to benefit from these treatments.

The functional and clinical outcomes of primary and metastatic malignancies of the elbow.

OBJECTIVES: This study aims to investigate the etiological distribution of primary and metastatic malignancies around the elbow and the effect of surgical and adjuvant treatments on clinical outcome. PATIENTS AND METHODS: Between January 2006 and December 2020, medical records of a total of 33 patients with elbow neoplasm (15 males, 18 females; median age: 55 years; range, 39 to 71 years) who underwent surgical treatment and with or without clinical treatment were retrospectively analyzed. The outcomes and frequencies of the elbow metastatic and primary malignancies were evaluated. Data were collected from patients' medical and radiological documents, and a dedicated archive was created for this study. RESULTS: Most tumors occurred on the right side and were intra-articular or distal to the humerus. A total of 75.8% (25/33) of the patients had tumors of any diameter ≥5 cm. Most patients were treated with extensive resection. A total of 81.8% (27/33) of the patients had wide resected tumor margins, and 18.2% (6/33) had intralesional tumor margins. The median follow-up was 42 (range, 1 to 83) months. Synovial sarcoma and malignant peripheral nerve sheath tumors were the most common soft tissue sarcomas, and pulmonary adenoma and multiple myeloma were found in metastatic lesions. CONCLUSION: Elbow surgery is particularly challenging due to the interrelationship of major neurovascular structures. Synovial sarcoma and malignant peripheral nerve sheath tumors are the most common soft tissue sarcomas, and pulmonary adenoma and multiple myeloma are found in metastatic lesions. Limb-sparing surgery is the gold-standard method recently.

Distribution Patterns of Benign and Malignant Bone and Soft Tissue Tumors and Tumor-like lesions in the Hindfoot and Ankle: A 12.5-year Analysis.

BACKGROUND/AIM: Benign and tumor-like lesions of the hindfoot and ankle are common, whereas malignant entities are rare. Accurate evaluation and timely management of these lesions can be challenging, making it crucial to understand their incidence and anatomic localization. This study retrospectively analyzed the distribution of benign and malignant bone and soft tissue tumors in the hindfoot and ankle. PATIENTS AND METHODS: This study included patient data from a single center, such as age, sex, histologic diagnosis, and anatomic location over a 12.5 year period. RESULTS: Of the 105 cases reviewed, 19 cases (18.1%) were osseous lesions and 86 cases (81.9%) were soft tissue lesions. The latter were divided into 77 benign and 9 malignant cases, resulting in an overall malignancy rate of 8.6%. The most common osseous lesion was the intraosseous ganglion (n=12). The majority of benign soft tissue lesions (75.3%) were located in the hindfoot, with TGCT, schwannoma, and ganglion cysts being the most common types. The nine malignant cases were distributed among seven entities and were evenly distributed among both regions and sexes. Malignant cases had a higher mean age (59.2 years) compared to benign cases (40.8 years; p=0.001). CONCLUSION: Tumors, tumor-like lesions, and pseudotumors represent an important aspect of ankle pathology. The majority of focal masses and swellings are benign soft tissue or osseous lesions, but malignant entities can occur and may be mistaken for benign conditions. Preoperative imaging and histopathologic examination are essential, and preoperative presentation to a multidisciplinary tumor board is recommended in unclear cases.

Importance of encouraging early presentation and referral for soft tissue lesions.

Delays in both the presentation and referral of soft tissue lesions have been extensively recorded in the existing literature. Such delays may result in lesions invading into surrounding tissues including neurovascular structures, increasing the risk of surgical complications and adverse consequences for patients. Delays in initiation of treatment of soft tissue sarcomas have further been associated with increased rates of metastasis. As such, patients' recovery may be limited due to late presentations, and residual morbidity may be more pronounced. This case report presents the predicament of a fungating mass in a female in her 80s in order to emphasise the importance of identifying and referring to such lesions early on. The referral delay of this lesion highlights the impact increasing awareness of this condition among both healthcare professionals and patients could have by allowing for earlier interventions.

EMA-Positive Superficial ALK-Rearranged Myxoid Spindle Cell Neoplasm Masquerading as Perineurioma/Hybrid Nerve Sheath Tumor.

ABSTRACT: Superficial anaplastic lymphoma kinase (ALK)-rearranged myxoid spindle cell neoplasm (SAMS) is a recently described entity which coexpresses ALK, CD34, and commonly S100. These neoplasms are characterized morphologically by concentric spindle cell whorls and cords and are commonly set in an abundant myxoid to myxocollagenous stroma, thus mimicking perineurioma or hybrid nerve sheath tumor. EMA immunostain has been reported to be negative in SAMS which helps in excluding the latter entities. Herein, we report the first EMA-positive SAMS of the right leg in a 37-year-old female patient masquerading as perineurioma/hybrid nerve sheath tumor. The tumor morphologically was comprised of spindle cells arranged in loose whorls and short fascicles set in myxoid to collagenous stroma and coexpressed CD34 and EMA, reminiscent of perineurioma. S100 showed focal staining. ALK immunostain was subsequently performed and was positive. ALK gene rearrangement was identified by fluorescence in situ hybridization break-apart assay and was further confirmed by next-generation sequencing-based RNA sequencing demonstrating FLNA::ALK fusion, thus supporting the diagnosis of SAMS. In conclusion, EMA can be expressed in SAMS, thus posing as a diagnostic pitfall. ALK immunostain and molecular studies are essential for confirming the diagnosis of SAMS and excluding potential mimickers, particularly perineurioma or hybrid nerve sheath tumor.

[Importance and implementation of radiological modalities in the diagnostics of soft tissue tumors]. / Bedeutung und Anwendung radiologischer Modalitäten in der Diagnostik von Weichteiltumoren.

Malignant soft tissue tumors, in particular, require a multimodal treatment concept involving interdisciplinary cooperation between radiologists, pathologists, surgeons and oncologists at special tumor centers. The foundations of the treatment decision are the imaging diagnostics and the diagnosis confirmation based on tissue samples. The (local) extent and growth behavior of a tumor are among the most important findings of imaging as they have a direct influence on the surgical procedure. The most important diagnostic procedure here is magnetic resonance imaging (MRI). The T1-weighted and fat-suppressed sequences after i.v. contrast administration are used to visualize the extent of the tumor. In synopsis with diffusion-weighted and T2-weighted sequences, a differentiation between vital tumor tissue and tumor necrosis is additionally possible. This also enables targeted sampling from vital tumor parts so that the patient can be assigned to the appropriate treatment concept as quickly as possible.

Extraskeletal Ewing Sarcoma Disguised as a Vascular Malformation.

Extraskeletal Ewing sarcoma (EES) is a rare entity, accounting for only 3% of lesions encountered in upper extremity. We present two paediatric patients, who were initially diagnosed with a vascular malformation based on clinical assessment and imaging. Final histopathology revealed Ewing sarcoma of soft tissue origin, confirmed by immunohistochemical analysis. Hand surgeons, who are routinely approached for a myriad of hand pathologies, should be wary and consider EES as a differential when treating such lesions. A multidisciplinary approach with an appropriate treatment algorithm can help in a speedy diagnosis, improving the long-term prognosis of the disease. Level of Evidence: Level V (Therapeutic).

Germline variants in patients diagnosed with pediatric soft tissue sarcoma.

BACKGROUND: While soft tissue sarcomas affect younger patients, few studies have assessed the distribution of underlying pathogenic germline variants. PATIENTS AND METHODS: We retrospectively identified all pediatric and young adult patients (0-22 years) at Haukeland University Hospital, Norway (1981-2019), through clinical and pathological records. We identified n = 46 eligible patients. From these 46 patients, adequate material representing normal tissue was available for n = 41 cases (n = 24 diagnosed with rhabdomyosarcoma, 9 with synovial sarcomas, 2 with Ewing sarcomas, and 6 without further classification), with matching tumor tissue for n = 40. Normal tissue samples were analyzed for germline pathogenic variants (PVs) by targeted sequencing of 360 cancer genes. RESULTS: Out of the 41 analyzed cases, we found PVs or likely PVs in 7 (17%). These variants were found in TP53, MUTYH, FANCC, DICER1, FANCA, MYO3A, and MYO5B. Supporting the causality of these PVs, four cases revealed loss of heterozygosity (LOH) of the wild-type allele in the tumor tissue, one patient with a PV in DICER1 had a second somatic variant in DICER1, and a patient with a PV in TP53 had the altered allele amplified in the tumor. For three out of five with available family history, a history of other cancers in relatives was recorded. Among genes with variants of uncertain significance, CHD1L was of particular interest, revealing a stop-gain and a missense variant. INTERPRETATION: A high fraction of young patients with soft tissue sarcoma harbor PVs. Among the genes affected, we substantiate a potential role of MYO5B and propose a potential role for MYO3A.

ISLET-1 expression in soft tissue neoplasms reveals high sensitivity but moderate specificity for desmoplastic small round cell tumors and potential utility as a diagnostic biomarker.

ISLET-1 (ISL1) is a LIM-homeodomain transcription factor. Selective ISL1 expression is shown in neuroendocrine, non-neuroendocrine, and some soft tissue tumors including desmoplastic small round cell tumor (DSRCT). We assessed the specificity of ISL1 (clone EP283, 1:500, Cell Marque) in 288 soft tissue tumors, which included 17 DSRCTs and other histologic mimics. Positive staining threshold for ISL1 was set to >10 % of neoplastic cell nuclei at moderate intensity. ISL1 IHC was positive in 15/16 (94 %) DSRCTs with 75 % showing diffuse (>50 %) expression. ISL1 was positive in 1/10 (10 %) Ewing sarcomas (EWS), 7/13 (54 %) alveolar rhabdomyosarcoma (RMS), 14/22 (63 %) embryonal RMS, 7/14 (50 %) synovial sarcomas, 15/16 (93 %) neuroblastoma, 1/5 (20 %) Wilms tumor, 2/4 (50 %) olfactory neuroblastoma, and all 9 Merkel cell carcinomas. Other tumors, including all CIC::DUX4 sarcomas, were negative except 3/27 leiomyosarcomas, and 1 each of angiosarcoma, myxoid liposarcomas, inflammatory myofibroblastic tumor, malignant peripheral nerve sheath tumor, tenosynovial giant cell tumor, dedifferentiated LPS, and 1 ectomesenchymoma. In summary, among the soft tissue tumors tested, ISL1 is a highly sensitive but moderately specific marker for DSRCT and may be useful to distinguish from round cell mimics including EWS and CIC::DUX4 sarcomas. The oncogenic role of ISL1 in these tumors warrants further investigation.

MUC5AC immunoreactivity in scattered tumor cells is useful for diagnosing CIC-rearranged sarcoma.

CIC-rearranged sarcoma is an aggressive round cell sarcoma, and an alternative ATXN1/ATXN1L fusion has been reported. Diagnosis may be difficult, and molecular assays may suffer from imperfect sensitivity. Characteristic histology and ETV4 immunohistochemical positivity are diagnostically helpful. However, ETV4 staining is unavailable in most laboratories. Here, we explored the diagnostic utility of MUC5AC immunohistochemistry in CIC-rearranged sarcomas. All 30 cases, except one, of CIC-rearranged sarcomas and 2 ATXN1-rearranged sarcomas were positive for MUC5AC, although the number of immunopositive cells was generally low (< 5%) in most samples, representing a characteristic scattered pattern. The only MUC5AC-negative case had the lowest tumor volume. Among the 110 mimicking round cell malignancies, 12 tumors showed MUC5AC positivity, including occasional cases of synovial sarcoma and small cell carcinoma, whereas the remaining 98 samples were negative. Despite its lower specificity than that of ETV4 and sparse reactivity that requires careful interpretation, MUC5AC may serve as a useful marker for CIC/ATXN1-rearranged sarcoma because of its wider accessibility.

Synovial hemangioma presenting with chronic painful infrapatellar mass: a case report.

BACKGROUND: Synovial hemangiomas are rare benign vascular anomalies surrounded by a synovial lining and were first described by Bouchut in 1856. These neoplasms can develop in the intra-articular region, resulting in effusions and knee pain. However, their cause remains unknown. Prompt diagnosis and intervention are critical to prevent chondral damage. Histopathological examination is used to achieve the diagnosis, which is often delayed because of a lack of specific clinical signs. This report describes a unique case in which a painful infrapatellar mass was diagnosed as a synovial hemangioma. The absence of typical magnetic resonance imaging (MRI) findings highlights the importance of arthroscopic excision for diagnosis and symptom relief. CASE PRESENTATION: A 20-year-old woman presented with persistent anterior left knee pain that became exacerbated when she climbed stairs. Despite previous pain management and physical therapy, she developed a painful lump beneath her patella that worsened over time. She had also undergone arthrocentesis, but this did not relieve her pain. Physical examination revealed a palpable, immobile 5-cm mass along the patellar tendon with limited knee flexion and extension and normal ligament stability. T1-weighted fat-saturated MRI of the left knee with gadolinium-based contrast revealed a lobulated intra-articular mass in Hoffa's fat pad that resembled a soft tissue chondroma. A biopsy of the mass was performed to provide histopathological evidence, confirming the benign nature of the mass. The subsequent excisional arthroscopy, combined with incision enlargement for mass removal, confirmed the histopathologic diagnosis of synovial hemangioma based on the presence of numerous dilated blood vessels and venous proliferation within sections of the synovium. Recovery was complete, and no residual tumor was detected on follow-up MRI after 1 year. CONCLUSION: This case study emphasizes the importance of arthroscopic excision over open surgery for patients with synovial hemangioma. The minimally invasive nature of arthroscopy combined with the well-encapsulated nature and location of the mass facilitates complete resection.