SPLENIC MICRO-ANATOMICAL LOCALIZATION OF SMALL LYMPHOCYTIC LYMPHOMA CHRONIC LYMPHOCYTIC-LEUKEMIA USING A NOVEL COMBINED SILVER-NITRATE AND IMMUNOPEROXIDASE TECHNIQUE

Small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) may be histologically difficult to differentiate from reactive lymphoid hy perplasia (RLH) in the spleen. Because routine hematoxylin and eosin ( H&E) staining delineates splenic microanatomy poorly, we have develope d a method that simultaneously stains reticulin fibers and B-lymphocyt es. B3 or formalin-fixed, paraffin-embedded archival splenic tissue wi th diagnoses of SLL/CLL (11 cases), RLH (10 cases), and trauma (seven cases) were studied using a novel silver nitrate immunoperoxidase (SNI P) double-staining technique. Gordon and Sweet's reticulin stain was f ollowed by immunoperoxidase staining for B-lineage marker CD20 (Dakopa tts, Carpinteria, CA) using the avidin-biotin method. This allowed us to clearly localize B cells to Malpighian bodies, periarteriolar lymph old sheaths, sinuses, or cords. Features identified by SNIP found onl y in SLL/CLL, but not in RLH or traumatized spleens, were trabecular i nfiltration (eight of 11 cases), subendothelial infiltration (seven of 11 cases), and prominent sinus involvement (seven of 11 cases). One o r more of these features were seen in 10 of 11 cases of SLL/CLL. Other distinguishing features were the percentage area occupied by B-lympho cytes in each section (SLL/CLL = 74%; RLH = 46%; traumatized spleens = 36%); and mean spleen weight (SLL/CLL = 1,603 g; RLH = 287 g; traumat ized spleens = 126 g). We have found the SNIP technique to be superior to traditional H&E staining in identifying B cells in the context of splenic microanatomy.