title: Intra-abdominal follicular dendritic cell tumour: a rare tumour in need of recognition.
abstract: OBJECTIVE
  Neoplasms of follicular dendritic cells are uncommon and the majority of them occur in lymph nodes. Rarely, they may occur inside the abdominal cavity. We describe two examples of intra-abdominal follicular dendritic cell (FDC) tumour. One involved the liver and the other involved the ampulla of Vater. Our aims are to complement the current understanding on this disease and to alert histopathologists and clinicians to this rare entity.
  
  
  RESULTS
  The clinical and radiological findings of the two cases of intra-abdominal follicular dendritic cell tumours were reviewed. The resected specimens were examined macroscopically and microscopically. Immunohistochemical studies, ultrastructural examination and in situ hybridization for Epstein-Barr virus were also performed. Both tumours could not be accurately diagnosed before pathological examination of the resected specimens. The soft to slightly firm consistency of the tumours resembled that of fixed brain tissue, and was distinctly different from hepatocellular carcinoma or pancreatic carcinoma. The fascicular arrangement of syncytial plump to spindle cells in a background of mixed inflammatory cells was the initial clue to the diagnosis, which was confirmed by the immunoreactivity of the tumour cells to follicular dendritic cell markers (CD21 and CD35), and by the demonstration of focal intercellular desmosome-like junctions between the complex cytoplasmic processes of the tumour cells. The tumour cells in the liver tumour also showed presence of Epstein-Barr virus on in situ hybridization study.
  
  
  CONCLUSIONS
  Awareness of the entity and the ability to recognize this tumour by histopathologists are emphasized because the tumour closely mimics a wide variety of other tumours and tumour-like lesions. Similar to the other reported FDC tumours of the liver, our case of hepatic follicular dendritic cell tumour is also positive for Epstein-Barr virus, suggesting that the virus may play a role in its pathogenesis.
authors.affiliation: Department of Pathology, University of Hong Kong, Queen Mary Hospital.
authors.forename: T W
authors.initials: TW
authors.lastname: Shek
authors.forename: C L
authors.initials: CL
authors.lastname: Liu
authors.forename: W C
authors.initials: WC
authors.lastname: Peh
authors.forename: S T
authors.initials: ST
authors.lastname: Fan
authors.forename: I O
authors.initials: IO
authors.lastname: Ng
mesh_terms: D000328:Adult; D014670:Ampulla of Vater; D000792:Angiography; D015703:Antigens, CD / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D003138:Common Bile Duct Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D003713:Dendritic Cells; D005260:Female; D004854:Herpesvirus 4, Human / Q000302:isolation & purification; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D008297:Male; D008875:Middle Aged
chemical_list: D015703:Antigens, CD; D014408:Biomarkers, Tumor