Synovial metastasis from lung cancer.

Intraarticular masses are infrequently encountered in clinical practice; however, the differential diagnosis can be broad. Neoplasia, both benign and malignant, and proliferative processes are the most common etiologies. We present a case of metastatic disease in the synovium in a patient with a history of lung cancer. Lung carcinoma is the most common primary malignancy to metastasize to synovial tissue, and the knee joint is the most common joint to be affected.