Validation at the protein level of the gene expression data through immunohistochemistry. (A) HRS cells of cHL lack expression of INPP5D/SHIP-1 as opposed to neoplastic cells of the other lymphomas (40× objective) and to non-neoplastic tonsilar follicular B cells (4× objective). Bar represents 500 μm. (B) The BIK protein is absent in HRS cells of cHL, while being mostly expressed by the neoplastic cells of the other lymphomas (for DLBCL, TCRBL, and BL also examples of negative cases are shown; 40× objective). In reactive tonsils, BIK is strongly and selectively expressed by GC B cells (4× objective). Bar represents 500 μm.