Localised hyaline vascular type of Castleman's disease mimicking adult-onset Still's disease

A previously healthy 18-year-old boy presented with daily spiking fever, polyarthritis, and evanescent skin rashes, as well as hepatomegaly and Raynaud's phenomena for 2 months. He was initially diagnosed with adult-onset Still's disease (AOSD). During the period of follow-up, intermittent fever and migratory polyarthritis persisted and an insidiously growing mass over the right axillary region was noted 1 year after the diagnosis of AOSD. Excisional biopsy of the mass revealed a group of lymph nodes with histological features of the hyaline vascular type of Castleman's disease. The patient's symptoms disappeared soon after excision of the lymph nodes.