CASE STUDIES IN DIAGNOSTIC IMAGING Series editor: V N Cassar-Pullicino Soft tissue mass around the shoulder

Clinical history A previously fit 47 year old female school teacher presented with a six month history of a painful swelling over her right shoulder. There was rapid development of the swelling initially, which then stabilised. On examination she was apyrexial with a large, firm, non-tender mass around the right shoulder, which clinically had some cystic features. There was no significant limitation of movement. Other findings on clinical examination included some minor soft tissue capsular swelling of the second and third metacarpophalangeal joints of the right hand. Otherwise the remainder of the locomotor system was normal. Her erythrocyte sedimentation rate was increased at 51 mm 1st h, but C reactive protein remained normal at <0.6. Full blood count was normal with a haemoglobin of 13.4 g/dl, white blood cell count 7.5 × 10 /l, platelet count 424 ×10/l. The rheumatoid factor, however, was positive with a titre of 1:1280.