Ab0770 a Rare Case of Synovial Metastasis Revealed by Knee Pain

Abstract

Background:Intra-articular masses are not frequently encountered in clinical practice. However, the differential diagnosis can be broad. Synovial metastasis is a rare presentation that carries a poor prognosis with a poor survival rate.Objectives:Here by a case of synovial metastasis of the knee joint in a patient diagnosed with an adenocarcinoma of the lung.Methods:A 60-year-old man with no remarkable past medical history presented to our department of rheumatology with right knee pain. He described a dull ache and swelling in his right knee with a dragging sensation, waking him up at night on a regular basis. The symptoms lasted from 6 months and were partially improved by analgesics and anti-inflammatory drugs. On examination, temperature was normal. The knee was edematous, erythematous, and warm with a range of motion of <90°. Laboratory investigations showed high acute phase reactants, the erythrocyte sedimentation rate was 75 mm. A plain radiograph of the left knee demonstrated a lytic lesion of the upper tibia. A magnetic resonance imaging of the right knee showed diffuse enlargement of the joint space due to a tissue infiltration within the synovium. These structures demonstrated heterogeneously increased T2 signal and intermediate T1 intensity characteristics. Most of the joint space was replaced by hyper enhancing synovium. At that time, differential considerations included severe inflammatory arthritis and synovial chondromatosis rather than unusual metastasis.Results:Biopsy concluded to synovial metastasis from primary adenocarcinoma. Further investigations were necessary. Chest tomography showed a tumor process of left lower lobe associated with mediastinal lymphadenopathy. The patient was treated with palliative external radiotherapy to the right knee. The evolution was marked by the appearance of multiple tracheobronchial fistulas. The patient died 3 months later due to the progression of the disease.Conclusion:We report a rare case of synovial metastasis concomitant to a lung adenocarcinoma. It is important to make a rapid diagnosis as early recognition of malignant infiltration into joints ensure appropriate multidisciplinary management decisions.Disclosure of Interests:None declared