Synovial sarcoma presenting as an intra-articular mass in a pediatric patient: a case report

Fig. 1. Plain radiograph of the concerned knee showing non-specific findings

Fig. 2. Axial T2 and coronal PD fat sat MRI scans of the left knee showing the lesion (red rows). Unfortunately, limited quality without gadolinium enhancement of the left knee as outside MR study were submitted as pre-op MRI. As well, no gradient cartilage sequences were included in the study. So, we were unable to comment about the above-mentioned sequences

Fig. 3. Intra-operative photograph showing a pedunculated 2 × 2 Cm small lesion, which appeared like a blood clot

Fig. 4. a Well-circumscribed nodule in the synovium (H&E staining, 2×) b Sub-synovial monomorphic spindle cell sarcoma (synovial lining is on the left side); (H&E staining, 10×). c Monomorphic spindle cell sarcoma with brisk mitotic activity (H&E stain, 20×). d Tumor cells showing patchy cytoplasmic positivity for cytokeratin 19 (immunohistochemistry CK19, 20×) e. Tumor cells showing diffuse nuclear positivity for TLE-1 (immunohistochemistry TLE-1, 20×). H&E: hematoxylin and eosin