Follicular dendritic cell sarcoma mimicking giant cell carcinoma of the pancreas.

Extranodal follicular dendritic cell (FDC) tumors are rare. Recognition of the morphological spectrum of FDC tumors is important to clinical diagnosis. Herein is presented a case of pancreatic FDC sarcoma with unusual clinicopathological features. A 64-year-old male patient presented with weight loss, poor appetite, abdominal fullness, mild anemia and mild peripheral eosinophilia. Histologically, the tumor was composed of both epithelioid and spindle cells with abundant intracytoplasmic hyaline globules. These tumor cells were positive for CD21, CD23, CD35, S-100 protein, fascin and clusterin. Both epithelioid and spindle tumor cells independently colonized the liver and formed two tumor nodules 18 months after the initial resection. Notably, the two hepatic metastases additionally acquired patchy expression of human leukocyte antigen-DR. The epithelioid FDC in one of the hepatic lesions transformed into numerous bizarre giant cells, which could easily be confused with a metastatic giant cell carcinoma from the pancreas. FDC tumor should therefore be included in the differential diagnoses when dealing with a giant cell tumor.