Bcl-3 staining of primary lymphomas (all immunoperoxidase with hematoxylin counterstain). (A) Strong nuclear expression of Bcl-3 in all neoplastic cells of an ALK-positive ALCL case with an intrasinusoidal growth pattern. (B) Variable expression intensity of Bcl-3 ranging from strong to intermediate in sheets of neoplastic cells of a further ALK-positive ALCL case. (C) The expression pattern of ALK-negative ALCL is similar to that of the ALK-positive cases. (D) The Hodgkin and Reed-Sternberg cells of a cHL case show a predominantly strong nuclear Bcl-3 expression. Also, cells of the surrounding inflammatory background infiltrate display a weak Bcl-3 expression. (E) Detection of a strong nuclear Bcl-3 expression in the L&H cells of an LPHL case accompanied by faintly labeled bystander cells. (F) Bcl-3 expression in the neoplastic cells of a DLBCL, whereas the numerous non-neoplastic smaller lymphocytes of the background infiltrate are completely Bcl-3 negative. (G) Within normal lymphoid tissue, a weak nuclear Bcl-3 expression is solely observed in follicular dendritic cells of germinal centers. (H) No Bcl-3–expressing cells are detectable in the white and red pulp of the spleen.