The major alteration in these cases involves the translocation of CCND2 (55–70% of cyclin D1-negative MCL) with an immunoglobulin gene, preferably with IGK and IGL rather than IGH. Most of the CCND2 translocations can be detected by break-apart probes (CCND2 or IGK/IGL). The gene discussed is CCND2; the disease is mantle cell lymphoma.