Hidden Threats around the Knee When Cysts Are Not Just Cysts: A Case-Based Expert Review
Abstract
Background: Soft tissue masses around the knee are commonly presumed to be benign cystic lesions. However, certain malignant tumors may mimic these entities, leading to delayed diagnosis and treatment. This case highlights the diagnostic challenges associated with malignant lesions presenting as common cysts.
Case Report: A 26-year-old woman presented with a painless mass in the posteromedial aspect of her left knee that had gradually enlarged over four months. Initial ultrasonography identified the lesion as a Baker’s cyst. Owing to atypical clinical and imaging features, further evaluation was pursued. The case was discussed at ORTHOBIT 2025 Congress (Tehran, Iran), where the diagnostic pathway, differential diagnoses, imaging findings, and management options were reviewed. Advanced imaging raised suspicion for a malignant soft-tissue tumor, emphasizing the limitations of relying solely on conventional imaging modalities.
Conclusion: Malignant tumors such as synovial sarcoma can closely resemble benign cystic lesions around the knee. Careful clinical assessment, recognition of atypical features, advanced magnetic resonance imaging (MRI) evaluation, and multidisciplinary collaboration are essential to avoid misdiagnosis and ensure timely management.
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19. Nydegger KN, Obergfell T, Heesen P, Schelling G, Studer G, Bode-Lesniewska B, et al. Planned and Unplanned Sarcoma Resections: Comparative Analysis of Local Recurrence, Metastasis, and Mortality. Cancers (Basel). 2024;16(19):3408. doi: 10.3390/cancers16193408. [PubMed: 39410028]. [PubMed Central: PMC11475640].
20. Allignet B, Pou P, Izarn F, Ray-Coquard I, Blay JY, Dufresne A, et al. Efficacy and Safety of Adjuvant Radiotherapy in Re- excised Soft-tissue Sarcoma After Unplanned Resection. Oncologist. 2023;28(7):633-9. doi: 10.1093/oncolo/oyad076. [PubMed: 36971503]. [PubMed Central: PMC10322143].
21. Gennaro N, Van der Loo I, Reijers SJM, Van Boven H, Snaebjornsson P, Bekers EM, et al. Heterogeneity in response to neoadjuvant radiotherapy between soft tissue sarcoma histotypes: associations between radiology and pathology findings. Eur Radiol. 2025;35(3):1337-50. doi: 10.1007/s00330- 024-11258-6. [PubMed: 39699680].
22. Özger H, Alpan B. Alternative to Extra-Articular Resection in Synovial Sarcoma of the Knee. In: Özger H, Sim FH, Puri A, Eralp L, Editors. Diagnosis and Treatment of Soft Tissue Tumors: Changes, Challenges and Strategies. Cham, Switzerland: Springer Nature 2025. p. 373-83.
2. Bakri A, Shinagare AB, Krajewski KM, Howard SA, Jagannathan JP, Hornick JL, et al. Synovial sarcoma: imaging features of common and uncommon primary sites, metastatic patterns,
https://jost.tums.ac.ir and treatment response. AJR Am J Roentgenol.2012;199(2):W208-15. doi: 10.2214/ajr.11.8039. [PubMed: 22826423].
3. Harish S, Lee JC, Ahmad M, Saifuddin A. Soft tissue masses with "cyst-like" appearance on MR imaging: Distinction of benign and malignant lesions. Eur Radiol. 2006;16(12):2652-60. doi: 10.1007/s00330-006-0267-5. [PubMed: 16670867].
4. Evenski AJ, Stensby JD, Rosas S, Emory CL. Diagnostic Imaging and Management of Common Intra-articular and Peri- articular Soft Tissue Tumors and Tumorlike Conditions of the Knee. J Knee Surg. 2019;32(4):322-30. doi: 10.1055/s-0038-1675609. [PubMed: 30449023]. [PubMed Central: PMC6445722].
5. Wang H, Zhang J, Bao S, Liu J, Hou F, Huang Y, et al. Preoperative MRI-Based Radiomic Machine-Learning Nomogram May Accurately Distinguish Between Benign and Malignant Soft-Tissue Lesions: A Two-Center Study. J Magn Reson Imaging. 2020;52(3):873-82. doi: 10.1002/jmri.27111. [PubMed: 32112598].
6. Shirodkar K, Hussein M, Balogh P, Azzopardi C, Botchu R. Painless knee mass in a young adult: answer. Skeletal Radiol. 2024;53(11):2551-4. doi: 10.1007/s00256-024-04682-8. [PubMed: 38642303].
7. Cho EB, Lee SK, Kim JY, Kim Y. Synovial Sarcoma in the Extremity: Diversity of Imaging Features for Diagnosis and Prognosis. Cancers (Basel). 2023;15(19):4860. doi: 10.3390/cancers15194860. [PubMed: 37835554]. [PubMed Central: PMC10571652].
8. Bermejo A, De Bustamante TD, Martinez A, Carrera R, Zabía E, Manjón P. MR imaging in the evaluation of cystic-appearing soft-tissue masses of the extremities. Radiographics. 2013;33(3):833-55. doi: 10.1148/rg.333115062. [PubMed: 23674777].
9. Chee DW, Peh WC, Shek TW. Pictorial essay: imaging of peripheral nerve sheath tumours. Can Assoc Radiol J. 2011;62(3):176-82. doi: 10.1016/j.carj.2010.04.009. [PubMed: 20510574].
10. Telischak NA, Wu JS, Eisenberg RL. Cysts and cystic-appearing lesions of the knee: A pictorial essay. Indian J Radiol Imaging. 2014;24(2):182-91. doi: 10.4103/0971-3026.134413. [PubMed: 25024531]. [PubMed Central: PMC4094974].
11. Shomal Zadeh F, Pooyan A, Alipour E, Hosseini N, Thurlow PC, Del Grande F, et al. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in differentiation of soft tissue sarcoma from benign lesions: a systematic review of literature. Skeletal Radiol. 2024;53(7):1343-57. doi: 10.1007/s00256-024-04598-3. [PubMed: 38253715].
12. Duan L, Huang H, Sun F, Zhao Z, Wang M, Xing M, et al. Comparing the blood oxygen level-dependent fluctuation power of benign and malignant musculoskeletal tumors using functional magnetic resonance imaging. Front Oncol. 2022;12:794555. doi: 10.3389/fonc.2022.794555. [PubMed: 36059651]. [PubMed Central: PMC9434553].
13. Crombé A, Spinnato P, Italiano A, Brisse HJ, Feydy A, Fadli D, et al. Radiomics and artificial intelligence for soft-tissue sarcomas: Current status and perspectives. Diagn Interv Imaging. 2023;104(12):567-83. doi: 10.1016/j.diii.2023.09.005. [PubMed: 37802753].
14. Rudd A, Pathria MN. Intra-articular Neoplasms and Masslike Lesions of the Knee: Emphasis on MR Imaging. Magn Reson Imaging Clin N Am. 2022;30(2):339-50. doi: 10.1016/j.mric.2021.11.011. [PubMed: 35512894].
15. Crombé A, Loarer FL, Alberti N, Buy X, Stoeckle E, Cousin S, et al. Homogeneous myxoid liposarcomas mimicking cysts on MRI: A challenging diagnosis. Eur J Radiol. 2018;102:41-8. doi: 10.1016/j.ejrad.2018.03.003. [PubMed: 29685543].
16. McCarville MB, Spunt SL, Skapek SX, Pappo AS. Synovial sarcoma in pediatric patients. AJR Am J Roentgenol. 2002;179(3):797-801. doi: 10.2214/ajr.179.3.1790797. [PubMed: 12185067].
17. Jamshidi K, Yahyazadeh H, Bagherifard A. Unusual Presentation of Synovial Sarcoma as Meniscal Cyst: A Case Report. Arch Bone Jt Surg. 2015;3(4):296-9. [PubMed: 26550597]. [PubMed Central: PMC4628639].
18. Blay JY, Soibinet P, Penel N, Bompas E, Duffaud F, Stoeckle E, et al. Improved survival using specialized multidisciplinary board in sarcoma patients. Ann Oncol. 2017;28(11):2852-9. doi: 10.1093/annonc/mdx484. [PubMed: 29117335]. [PubMed Central: PMC5834019].
19. Nydegger KN, Obergfell T, Heesen P, Schelling G, Studer G, Bode-Lesniewska B, et al. Planned and Unplanned Sarcoma Resections: Comparative Analysis of Local Recurrence, Metastasis, and Mortality. Cancers (Basel). 2024;16(19):3408. doi: 10.3390/cancers16193408. [PubMed: 39410028]. [PubMed Central: PMC11475640].
20. Allignet B, Pou P, Izarn F, Ray-Coquard I, Blay JY, Dufresne A, et al. Efficacy and Safety of Adjuvant Radiotherapy in Re- excised Soft-tissue Sarcoma After Unplanned Resection. Oncologist. 2023;28(7):633-9. doi: 10.1093/oncolo/oyad076. [PubMed: 36971503]. [PubMed Central: PMC10322143].
21. Gennaro N, Van der Loo I, Reijers SJM, Van Boven H, Snaebjornsson P, Bekers EM, et al. Heterogeneity in response to neoadjuvant radiotherapy between soft tissue sarcoma histotypes: associations between radiology and pathology findings. Eur Radiol. 2025;35(3):1337-50. doi: 10.1007/s00330- 024-11258-6. [PubMed: 39699680].
22. Özger H, Alpan B. Alternative to Extra-Articular Resection in Synovial Sarcoma of the Knee. In: Özger H, Sim FH, Puri A, Eralp L, Editors. Diagnosis and Treatment of Soft Tissue Tumors: Changes, Challenges and Strategies. Cham, Switzerland: Springer Nature 2025. p. 373-83.
| Files | ||
| Issue | Vol 12 No 3 (2026) | |
| Section | Case Report | |
| Keywords | ||
| Synovial Sarcoma Cyst Knee Soft Tissue Sarcoma Magnetic Resonance Imaging | ||
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How to Cite
1.
Saberi S, Khabiri SS, Valinejad A. Hidden Threats around the Knee When Cysts Are Not Just Cysts: A Case-Based Expert Review. J Orthop Spine Trauma. 2026;12(3):148-50.
