Cyclin D1-negative mantle cell lymphoma.

Cyclin D1-negative mantle cell lymphoma (MCL) is regarded as a B-cell neoplasm that has morphologic and immunophenotypic findings indistinguishable from typical MCL. These neoplasms lack cyclin D1 overexpression by immunohistochemistry and t(11;14)(q13;q32)/IGH::CCND1. Since cyclin D1-negative MCL was first recognized by gene expression profiling in 2003, there has been diagnostic confusion regarding this entity, mostly attributable to a lack of diagnostic tools to recognize these neoplasms in most clinical laboratories. Accumulated data show that most cyclin D1-negative MCL cases harbor CCND2 or CCND3 translocation with a variety of gene partners. In this review, the concept of cyclin D1-negative MCL is discussed in chronological order to further our understanding of this entity. We then discuss currently available diagnostic approaches and we conclude with future directions. We also suggest that the more specific terms CCND2-rearranged MCL or CCND3-rearranged MCL be used for neoplasms in which the rearranged gene is known, and that we reserve the term cyclin D1-negative MCL for neoplasms in which the rearranged gene in unknown.