Calcified synovial metastasis in the knee from renal cell carcinoma: a case report.

We present the case of an 83-year-old man who had painful swelling of right knee for 6 months. Radiographs showed a large intra-articular soft-tissue mass with small calcifications, whereas MRI detected a multilobulated intra-articular tumor with bone erosions at the distal femur. Histopathology of ultrasound-guided biopsy specimen of the synovial mass revealed it to be a poorly differentiated metastatic carcinoma. Abdominal computed tomography with intravenous contrast medium administration found a heterogeneously enhancing large right renal mass with calcifications, which was shown to be a renal cell carcinoma on histopathology. No metastases were found elsewhere. To our knowledge, this is the first reported case with MRI findings of a calcified intra-articular synovial metastasis from renal cell carcinoma.