Figure 1: Sagittal (left) and axial (right) MRI of right elbow revealing widespread hypertrophic synovitis, reducing intra-articular volume and compressing adjacent structures such as the ulnar nerve.
was negative both EGFR and KRAS. The chemotherapy regimen of folinic acid, fluorouracil, oxaliplatin (FOLFOX), and cetuximab was initiated. Localized radiation therapy to the right elbowwas also incorporated in the treatment plan. Four months post-arthroscopy, a new lung mass developed. Seven months post-arthroscopy, the patient presented with recalcitrant elbow pain. Physical exam re- vealed cachexia, wrist drop, and severely diminished ROM. Radiographs revealed pathologic fracture of the humerus, and trans-humeral amputation was performed three weeks later. Pathologic examination of the limb showed a 9.7 cm mass of the synovium, which spread to the distal humerus, proximal ulna, proximal radius, and surrounding muscles but with no nerve or blood vessel involvement. The patient reported improved quality-of-life, controlled pain, and de- nied phantom pain post-surgery. The patient continued on chemotherapy for his lung mass and died from its sequalae five months post-amputation, one year following the diag- nosis of synovial metastasis. DISCUSSION Unilateral joint pain can present in a variety of ways, including gout, chondrocalcinosis, avascular osteonecrosis, septic arthritis, autoimmune arthropathies, and cancer. Pri- mary malignancies, metastasis, paraneoplastic syndromes, or antineoplastic therapies are possible etiologies for joint pain associated with cancer. 2 Synovial metastasis is rare, with only 49 cases reported in the literature. 6 Synovial me- tastasis is postulated to occur through either hematologic spread or adjacent bone invasion. This metastatic invasion
is typically aggressive and often presents with concurrent bone and soft tissue involvement. The average post-diag- nosis survival time is less than six months. 1,2 Synovial metastasis usually presents as an acute-to- subacute joint pain not relieved by NSAIDs or narcotics. The knee is by far the most common site of synovial metas- tasis (>50%). The lung is the most common site of primary disease, followed by the colon. From both sources, the his- topathology is most commonly adenocarcinoma. Synovial metastasis from the breast is extremely rare, and prostatic metastasis has not been reported. 1,2 Investigation of whether lung and colon cancers have a predilection for synovial tis- sue or if synovial metastasis results because of the frequency of these common etiologies is an area for future research. Radiographs, MRIs, and CTs have a limited role in diagnosing synovial metastasis, often with nonspecific findings such as synovitis and bursitis. As with the case at hand, the synovium is often intermediate intensity on T1-weighted imaging and hyperintense on T2-weighted imaging. 3,4,6 MRIs and CTs are useful once malignancy is diagnosed to assess surrounding tissue pathology and peri- articular infiltration. 3,7 Nuclear imaging techniques, such as 99m Technetiumpyrophosphate bone scans, have been useful in some cases, demonstrating increased uptake in the intra- articular synovium. 7,8 Biopsy of synovial tissue with subsequent pathologic workup is required for definitive diagnosis of synovial me- tastasis. 4,5 Once common joint pathologies are ruled out, the first step to investigate suspected synovial metastasis should be clinical joint aspiration. Although it was negative in the
J La State Med Soc VOL 166 March/April 2014 51
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