Insertion of the CCND1 gene into the IgH locus in a case of leukaemic small cell mantle lymphoma with normal chromosomes 11 and 14.

The t(11;14)(q13;q32) translocation is considered to be the cytogenetic hallmark of mantle cell lymphoma. This report describes a case of leukaemic mantle cell lymphoma in which conventional cytogenetics on stimulated peripheral blood cells showed a 46,XY, t(1;12)(p21;q23)/46,XY karyotype. Fluorescence in situ hybridisation analysis using a dual colour immunoglobulin heavy chain (IgH)/CCND1 probe showed a fusion hybridisation signal on one normal chromosome 14, indicating that an insertion of the CCND1 gene into the 14q32/IgH locus had taken place. Overexpression of the cyclin D1 protein was demonstrated on bone marrow trephine by immunohistochemical staining.