80 yrs female with DLBCL of mandibulla, diagnosed in 2005 May.  
REVIEW: Slightly nodular and fibrotic picture with large lobated cells. IH: CD20+; Bcl6+; Mum-/+; CD10(-); Bcl2+/- (faint); CD30+; LCA+; CD21/CD23(-)(FDCs absent);CD15(-); Pax5+.  
In 2008 March 12cm tumor closed to adrenal projection between right kidney, liver, v. cava inferior was biopsied. Pathology diagnosis: Mesenchymal tumor, more probable high grade GIST with IH: CD117(-)(sic!), CD34/AsmActin/Desmin(-), S100-/+.  
HISTO: Low grade spindle cell tumor. Duodenum mucosa/m. propria and pancreatic tissue closed to tumor.  
REVIEW AND EXPANDED IH in 2009 under request of GIST registry as CD117 negative GIST.  
IH SUMMARY: Vimentin+, EMA+, CD68+, CD23+, CD21+, S100-/+, LCA-/+(?), CD3/CD20/CD34/CD117/PanCK/AsmActin/CD31(-), CD1a(-). Ki67 <5%.  
VIRTUAL SLIDE: Aperio.  
 
PROPOSAL: Retroperitoneal (?) folicullar dendritic cell tumor/sarcoma.  
QUEST: Relations of primary bone DLBCL and FDC tumor (single clone? transdifferentiation? coincidence?).  
ADDITIONAL MATERIALS ARE APPENDED AS EXAMPLES OF DIFFERENTIAL DIAGNOSTICS OF GI TRACT SPINDLE CELL AND DENDRITIC CELL LESSIONS ONLY.  
 
Series of these 2 cases are dedicated to Basel hematopathology team. It's pleasure be with you on the web.