FDG PET/CT in follicular dendritic cell sarcoma with extensive peritoneal involvement.

Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm that originates from follicular dendritic cells. A 33-year-old woman was referred because of a 2-month history of lower abdominal fullness. Enhanced T1-weighted MR images showed enhancement of the thickened pelvic peritoneum. FDG PET/CT was performed showing multiple FDG-avid lymph nodes in the parapharyngeal, bilateral supraclavicular, left axillary, mediastinal, and abdominal regions, and intense FDG uptake in the thickened mesentery and peritoneum. Pathologic findings of both the left supraclavicular lymph node and peritoneal biopsy specimens were consistent with high-grade FDCS. In this case, extensive peritoneal involvement by FDCS was unusual.