Intense 18F-FDG Uptake in Isolated Splenic Rosai-Dorfman Disease

A 66-year-old woman with left upper abdominal pain had a solitary splenic mass nearly inconspicuous on unenhanced CT but progressively enhancing, although hypoattenuating relative to adjacent splenic parenchyma, on contrast-enhanced CT. 18 F-FDG PET/CT showed intense uptake (SUVmax, 15.1) without additional suspicious hypermetabolic foci within the imaged field of view. CT suggested a potentially malignant splenic neoplasm, with lymphoma among the preoperative considerations. Splenectomy confirmed Rosai-Dorfman disease. No recurrence was identified on CT at 10 months. This case illustrates the broad differential diagnosis of solitary FDG-avid splenic masses.