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Follicular dendritic cell sarcoma with microtubuloreticular structure and virus‐like particle production in vitro

Neoplasm of follicular dendritic cells (FDC), follicular dendritic cell sarcoma (FDCS), is a rare tumor of intermediate to high‐grade malignancy in lymph nodes and visceral organs. Reported herein is a case of FDCS arising from cervical lymph nodes in a 16‐year‐old Japanese boy, who died of the disease 3 years after diagnosis. The tumor cells were pale eosinophilic and elongated with euchromatic nuclei and were positive for CD21, clusterin, and CNA‐42 on immunohistochemistry, as well as desmosome‐like junctions on electron microscopy. The presence of microtubuloreticular structures (MTRS) in the tumor cells and associated lymphocytes characterized this case, suggesting some viral infection, although qualitative polymerase chain reaction of genomic and complementary DNA obtained from the tumor failed to demonstrate any viral infection at the laboratory level. The stimulation of dispersed tumor cells and peripheral blood mononuclear cells with mAb to CD3 and interleukin‐2 was attempted; and the cell line established by the authors (FDCS‐Sa) was stimulated with iododeoxyuridine. Virus‐like particles (VLP) were successfully induced from each cellular source. The VLP, 100 nm in diameter, showed an electron‐dense thorny envelope and granular core. This is the first case of FDCS with MTRS accompanying VLP production in vitro.