CCND1 and mantle cell lymphoma: These results are of pathogenic relevance considering that although expressed at mRNA level at extremely low extent,[39] cyclin D1 protein is not regularly expressed in normal B cells, as cell cycle is mostly regulated by cyclin D2 and cyclin D3 in these cells.[40] Moreover, these data suggest that cooperation between a CD40L-rich microenvironment, that characterizes MCL,[41] and a chronic TLR stimulation may have an important role in promoting and/or supporting lymphomagenesis of MCL, where cyclin D1 is constitutively expressed.