Background and Aim: The cytogenetic and diagnostic hallmark of mantle cell lymphoma (MCL) is translocation t(11;14)(q13;q32), resulting in overexpression of cyclin D1. Cyclin D1 expression was analysed in 32 cases of MCL.

Methods: The t(11;14) translocation was detected by fluorescence in situ hybridisation, level of cyclin D1 mRNA by competitive RT-PCR, and level of cyclin D1 and D2 proteins by immunohistochemistry and/or immunoblotting.

Results: In 30 cases, the presence of translocation t(11;14), a high level of cyclin D1 mRNA, and a high level of the cyclin D1 protein were confirmed. Two cyclin D1-negative cases overexpressing cyclin D2 were detected by immunoblotting.

Conclusions: There are rare cyclin D1-negative cases of MCL overexpressing cyclin D2. Anti-cyclin D1 antibodies with low specificity can bind both cyclin D1 and cyclin D2, thus providing false cyclin D1-positive signals in immunohistochemical analysis.