FDG PET/CT in Duodenal Follicular Dendritic Cell Sarcoma.

Follicular dendritic cell sarcoma (FDCS) of the duodenum is extremely rare. We describe the contrast-enhanced CT and FDG PET/CT findings in a case of duodenal FDCS. Contrast-enhanced CT revealed a large, irregular mass originating from the horizontal portion of the duodenum. The mass demonstrated heterogeneous enhancement, with internal areas of low-attenuation necrosis and coarse calcifications. The mass showed significantly increased FDG uptake. The patient underwent surgical resection, and histopathologic examination revealed a spindle cell tumor positive for CD21 and CD35, confirming the diagnosis of FDCS.