ABSENCE OF CYCLIN D1 PROTEIN EXPRESSION IN SPLENIC MARGINAL ZONE LYMPHOMA

Splenic marginal zone lymphoma (SMZL) is a recently recognized primary splenic lymphoma SMZL can be associated with peripheral lymphocytosis , in which some cells have a villous morphology (splenic lymphoma with villous lymphocytes [SLVL]). Several recent studies suggested involve ment of the bcl-1 locus and/or the cyclin D1 gene, located on chromoso me 11q, in SMZL/SLVL. Translocation t (11;14) is associated with rearr angement of the bcl-1 locus and overexpression of the cyclin D1 gene. Both the translocation and cyclin D1 protein expression are characteri stic of mantle cell lymphoma (MCL) and are rare in other lymphoid neop lasms; thus, their detection is useful in the diagnosis of MCL. Becaus e the differential diagnosis of low-grade lymphoma in the spleen can b e difficult, it is important to assess the frequency of cyclin D1 expr ession in SMZL to determine its usefulness in differential diagnosis f rom MCL, We analyzed the expression of cyclin D1 nuclear protein in pa raffin sections using an immunoperoxidase technique in 17 cases diagno sed as SMZL. In eight cases, the presence of cyclin D1 mRNA was also a ssessed by Northern blot analysis. None of the 17 cases of typical SMZ L showed expression of cyclin D1 mRNA or protein. In contrast, four ca ses used as controls showed either expression of cyclin D1 protein or mRNA or both. We conclude that assessment of cyclin D1 protein express ion can be useful in distinguishing SMZL from MCL involving the spleen .