A 5-year-old boy with unicentric Castleman disease affecting the mesentery: utility of serum IL-6 level and (18)F-FDG PET for diagnosis.

Castleman disease (CD) is a rare lymphoproliferative disorder of unknown etiology. It is quite difficult to diagnose CD without typical localized signs or symptoms. We present a 5-year-old boy with unicentric plasma cell CD in the mesentery, which was too small to be detected by any conventional imaging. (18)F-fluorodeoxyglucose positron emission tomography image and a serum cytokine profile prompted us to perform a curative surgical excision, confirming his diagnosis. Our case also supported an important role of interleukin-6 in the pathophysiology of plasma cell CD.