Cryptic Insertions Of The Immunoglobulin Light Chain Enhancer Region Near CCND1 In T(11;14)-Negative Mantle Cell Lymphoma

Cyclin D1+ mantle cell lymphoma (MCL) is molecularly characterized by the t(11;14)(q13;q32) or rearrangements of CCND1 gene with the immunoglobulin (IG) light chains.1,2 Most MCL can be diagnosed based on the characteristic pathologic features and cyclin D1 expression without the need for demonstrating the genetic translocation. However, in cases with atypical morphologic or phenotypic features other B-cell neoplasms that sometimes also have cyclin D1 positivity may be in the differential diagnosis.1 In these situations the detection of the CCND1 rearrangements may assist in the diagnosis since most other lymphomas do not carry translocations of the gene.3-7 A subset of plasma cell myelomas express cyclin D1 associated with the t(11;14) but are usually not in the differential diagnosis of MCL and are SOX11- negative.5 Nevertheless, there are occasional lymphoid neoplasms with MCL features in which cyclin D1 is strongly expressed without an apparent gene rearrangement using conventional cytogenetics or fluorescence in situ hybridization (FISH) with fusion or break-apart probes. The mechanisms of cyclin D1 overexpression in these cases are unclear and the MCL diagnosis may be questioned