Histological and immunohistochemical features of cHL cases with CD8_CXCR5+ICOS+T cells. Low power views (hematoxylin and eosin [H&E] stain, original magnification ×25) of 2 different cHL cases with CD8_{CXCR5+ ICOS+} cells show a similar pattern of nodular architecture, with only scant fibrotic foci (A-B). There was no nodular sclerosis. A variable number of hyperplastic and/or disrupted GCs were present (C, original magnification ×100; H&E stain), and surrounded by neoplastic Reed-Sternberg (RS) cells (C, arrow). CD30 (D, original magnification ×100) and Bcl-6 (E, original magnification ×400) immunostainings highlighted the close vicinity between neoplastic cells (CD30⁺ cells in panel D and arrow in panel E) and GC cells, whereas the mantle zone was deficient (dotted circle on panels C-E). The cell composition of most nodules included a majority of reactive lymphocytes and scattered RS cells (F, original magnification ×50; F1, original magnification ×400; H&E stain), though some eosinophils could be focally observed (F2, original magnification ×400; H&E stain). A few nodules considered as CD8-rich contained high numbers of CD8⁺ cells surrounding numerous RS cells (G, original magnification ×25; G1, original magnification ×200). However, most nodules were considered as CD8-poor, because they contained only scarce CD8 T cells (G; G2, original magnification ×400). ICOS immunostaining (H, original magnification ×25) on a serial section showed that CD8-rich nodules displayed strong ICOS expression (H1, original magnification ×200), whereas ICOS expression was weak in CD8-poor nodules (H2, original magnification ×200) with a distribution evocative of CD4 T_FH rosetting. Double fluorescent immunostaining (panel I, original magnification ×600) shows ICOS (green) and CD8 (red) coexpression at a single-cell level (yellow) in CD8-rich nodules.