(A and B) Parallel sections of a hyperplastic lymph node stained for BSAP and CD20 in (A) and for BSAP and CD3 in (B). In (A), BSAP expression (brown nuclear staining) is shown restricted to the CD20 positive B cells (purple-black) that are localized mainly in the germinal center and mantle zone (lower half of both photomicrographs), whereas the CD3⁺ (purple-black) interfollicular T cells in (B) are essentially negative for BSAP. (C and D) Mantle cell lymphoma stained for BSAP (brown) and CD20 (purple-black) in (C) and BSAP (brown) and CD3 (purple-black) in (D). The CD20⁺ tumor cells are strongly positive for BSAP, whereas the CD3⁺ T cells are BSAP negative. (E and F) Mediastinal large-cell lymphoma stained for BSAP and CD20 in (E) and BSAP and CD3 in (F). The CD20⁺ tumor cells stain strongly for BSAP, whereas the nonneoplastic infiltrating CD3⁺ T cells are negative for BSAP. (G) FL, grade 1 stained for BSAP (brown) and CD3 (purple-black). Note the occasional CD3⁺, BSAP-negative T cells, and rare CD3⁻ BSAP-negative cells that most likely represent dendritic cells. (H) AILD-like T-cell lymphoma stained for BSAP (brown) and CD20 (purple-black). The tumor cells are negative for BSAP, whereas 2 residual B cells show nuclear BSAP staining and membrane CD20. (Original magnifications [A] ×400, [B] ×400, [C] ×400, [D] ×400, [E] ×1,000, [F] ×1,000, [G] ×1,000, and [H] ×1,000.)