Right knee pain for 3 years and a mass lesion gradually increasing in size over 4 months.
The patient was admitted with a history of right knee pain for 3 years and a mass lesion gradually increasing in size over 4 months. On physical examination, the right knee was swollen and red. On laboratory examination, there was no remarkable finding except elevated sedimentation rate. On lateral plain radiographies of the right knee, we detected a soft tissue density around the knee joint and tibia. There were extensive calcifications within the lesion. The cortical surface of the tibia neighboring the lesion was invased (Fig 1). Axial computed tomography (CT) sections through the right knee and proximal tibia showed an isodense mass lesion around the knee joint and tibia. Marked stippled and lineer calcifications were also detected within the lesion. (Fig 2). Sagittal spin-echo T1-weighted magnetic resonance (MR) imaging showed a heterogeneous isointense mass lesion relative to muscle tissue. Calcifications were detected as signal voids (Fig 3a). On gradient-echo T2-weighted images, the lesion was heterogeneous hyperintense. There was a pseudocapsule appearance at the anterior surface of the lesion (Fig 3b). T1-weighted images after contrast medium injection showed marked enhancement at the lesion and there was heterogeneous enhancement within the medullar portion of the tibia due to direct tumoral invasion (Fig 3c). Histopathologic evaluation of biopsy and surgery material confirmed the diagnosis of synovial sarcoma.
Synovial sarcoma is a rare tumor that constitutes approximately 10% of all soft tissue sarcomas. It is most common in 2nd and 4th decade of life but may be seen in all age groups (1). The name of the synovial sarcoma originates from the similarity of the synovials cells that lay the joint surface. Synovial sarcoma locates mostly in tendons and bursas in close proximity to joints. It generally involves lower extremity but may be seen at upper extremities, head and neck region, the wall of the abdomen, and ankle. On plain radiographies, soft tissue densities with well-defined contours can be detected in 67 % of the cases located near the joints. Calcifications can be seen in 30 % of the cases. Bone invasion is detected in 20% of the cases. The lesion shows increased densities than muscles on CT. CT is best in demonstrating cortical bone involvement and calcifications than MR imaging. Although it is not possible to make a specific diagnosis with MR imaging, there are some described imaging features in literatures. Synovial sarcoma can be seen as heterogeneous multiloculated mass lesion with internal septations. The contour of the lesion is generally well-defined and may have a capsule formation (1-3).The MR imaging characteristics of synovial sarcoma are nonspesific, a relatively well-defined juxtaarticular mass, often of great size with signal intensity mainly intermediate on T1-weighted and intermediate on T2-weighted images. Synovial sarcoma shows intense but heterogeneous gadolinium enhancement. The existence of hemorrhagic components, fluid-fluid levels and areas that are hyper-, hypo-, isointense relative to fat (triple signal) on T2-weighted images in a mass located close to a joint tendons and bursa may suggest diagnosis (4). Recent studies about the dynamic Gd-enhanced imaging in synovial sarcomas showed enhancement of synovial sarcomas within 7 s after arterial enhancement (5). This finding was found to be a consistent sign mostly encountered in this tumor MR imaging demonstratesbone infiltration in 21-28% of case. The differential diagnosis of these lesions should mainly include other sarcomas. It is important to remember that small, well-defined, homogeneous lesions may mimic cystic or solid benign lesions (4)
Synovial sarcoma
The patient is a 17-year-old female with a chief complaint of right knee pain for three years. Over the last four months, a palpable mass has been noted, which has gradually enlarged. Based on the provided X-ray, CT, and MRI images, the main features are as follows:
Based on the above imaging characteristics, the lesion is a large soft tissue mass located near the joint, with relatively clear boundaries but also showing calcifications and bone involvement, which aligns with imaging features of a high-grade soft tissue malignancy.
Considering the patient's age (17 years old), clinical presentation (a soft tissue mass near the joint, pain for three years, rapid enlargement in recent months), and imaging findings, the potential diagnoses and differential diagnoses include:
Taking into account the patient’s age, local symptoms (long-term knee pain with a gradually enlarging mass), imaging findings (calcifications, bone destruction, enhancement pattern, periarticular soft tissue mass), and typical features reported in the literature, synovial sarcoma is the most likely diagnosis. However, it must be emphasized that definitive diagnosis requires pathological and immunohistochemical testing to confirm the tumor type.
Note: If the patient has bone fragility, compromised cardiopulmonary function, or is undergoing chemotherapy or radiotherapy, exercise forms and intensities should be chosen carefully. It is recommended to proceed under the guidance of a multidisciplinary rehabilitation team.
Disclaimer: This report is for reference only, based on the currently provided imaging data and medical history. It does not replace an in-person consultation or the opinion of a professional doctor. For further questions, please consult an orthopedic or oncologic surgeon, and combine pathology, molecular testing, and comprehensive clinical evaluation for final management.
Synovial sarcoma
