E09. LYMPHOMA OR ADULT-ONSET STILL’S DISEASE? A CASE OF A LARGE PLEURAL MASS

Abstract

Background: We present a case of a large progressive inflammatory pleural mass, in a 57 year old man with a long-standing diagnosis of adult onset Still's disease (AOSD) (meets Yamaguchi criteria with persistent fever, arthritis, rash, lymphadenopathy and negative RhF and ANA, albeit with a normal serum ferritin). He has been treated for many years with methotrexate (MTX) orally 15mg once weekly, with intermittent courses of oral prednisolone. He presented with loss of disease control, following patient discontinuation of MTX due to a sustained period of remission. He had active inflammatory arthritis and enthesitis, paraesthesia in lower limbs, fatigue, night sweats and Raynauds phenomenon, all of which persisted despite re-commencing MTX in escalating doses and the addition of leflunomide. A PET-CT scan demonstrated a pathological, irregular pleural mass, with increased FDG uptake, involving a large area of pleura at the base of the right lung. The mass extended into the retrocrural space, and to the right of the descending aorta, where it displaced the coeliac axis. Images were discussed by the regional lymphoma MDT, who felt lymphoma to be the most likely diagnosis, though tissue biopsy would be necessary. DMARDs were suspended. Following two unsuccessful attempts at US-guided biopsy, he proceeded to VATS biopsy. Intermediate imaging showed enlargement of the mass, which had become contiguous with soft tissue around the oesophagus and extended inferiorly on both sides of the aorta, up to the mid-body and neck of the pancreas. There was progressive lymphadenopathy in the coeliac and para-aortic nodes. Methods: Following analysis at a sub-specialist histology unit he was diagnosed as having benign pleuritis, though with an unusually large degree of thickening in the pleura. Results: He was re-commenced on prednisolone, MTX and leflunomide without achieving disease control, though subsequent treatment with tocilizumab has led to rapid resolution of all symptoms and normalisation of inflammatory markers. Conclusion: In patients with longstanding autoimmune disease, a loss of disease control should raise concerns of lymphoma, and lead to appropriate investigation. This is an unusual case of a large benign inflammatory pleural mass extending to surround the oesophagus, aorta and pancreas, mimicking lymphoma in a patient with AOSD. Pericarditis, pleuritis, pleural effusion and transient pulmonary infiltrates have been observed in 30 to 40 percent of patients with AOSD, though rarely has such a large pleural mass been described.