p27 and cyclin D3 expression in reactive and tumor lymphoid tissue. Germinal center cells show low levels of p27 expression (A) with opposed high cyclin D3 staining (B). DLBCL case with a low level of p27 expression restricted to small lymphocytes (C); and cyclin D3–negative (D). DLBCL case with high simultaneous expression of p27 (E) and cyclin D3 (F) in tumor cells.