What are the accepted direct associations between musculoskeletal syndromes and malignancy?
Metastatic disease, leukemia, lymphoma, and primary synovial and bone tumors are directly associated with the pathologic mechanisms of the underlying tumor. Bone metastases typically involve the long bones, spine, or pelvis and generally arise from breast, lung, and prostate more than kidney and thyroid neoplasms. The majority of skeletal metastases do not produce pain. Metastases or carcinomatous invasion of the synovium may rarely be the initial manifestation of a malignancy. Lung neoplasms are the most common primary tumor. Large joints are most likely to be involved with monoarthritis of the knee, the most common presentation. Metastases to joints distal to the elbows and knees are very rare and usually due to lung cancer. Severe joint pain especially at night with a noninflammatory (monoarticular predominance) or hemorrhagic joint effusion that rapidly reaccumulates after aspiration should suggest carcinomatous invasion of the synovium. Synovial fluid cytology and/or synovial biopsy will be diagnostic.
