CCND1 and mantle cell lymphoma: In follicular lymphoma (FL) and mantle cell lymphoma (MCL), immature B lymphocytes in BM are considered the origin of tumor cells; the reciprocal cTr between IgH and oncogenes such as BCL-2 on chr 18 or CCND1 on chr 11 during VDJ rearrangement is responsible for tumorigenesis of B lymphocytes18.