The translocation juxtaposes sequence of Ig heavy chain gene (IGH) with the BCL-1 locus, which results in the CCND1 gene up-regulation and, in turn, cyclin D1 overexpression (Rimokh et al., 1993; de Boer et al., 1995; de Boer et al., 1995); although concordancy was not shown between overexpression of cyclin D1 and t (11; 14) (q13; q32) in MCL cases (Leroux et al., 1991; Vandenberghe et al., 1992). This evidence concerns the gene CCND1 and mantle cell lymphoma.