Mantle cell lymphoma is characterized by a t(11;14)(q13;q32) translocation resulting in cyclin D1 protein overexpression. Immunohistochemical detection of the latter, therefore, is a useful marker for the diagnosis of mantle cell lymphoma. Nevertheless, interpretation of results is often hampered by the weak immunoreactivity obtained with routine detection techniques. This problem can be overcome by resorting to highly sensitive catalyzed signal amplification methods based on peroxidase-catalyzed deposition of a biotinylated phenolic compound. The present study compares the results obtained with catalyzed signal amplification, labeled streptavidin biotin, and dextran polymeric conjugate (EnVision+) techniques in cyclin D1 demonstration in mantle cell lymphoma. The study was performed on formalin-fixed, paraffin-embedded archival tissue from 20 mantle cell lymphoma cases. Ten cases of small lymphocytic lymphoma and 10 instances of follicular center cell lymphoma were used as controls. Antigen retrieval was done by autoclaving under controlled pressure (2 bar) and temperature (120 degrees C) conditions. The best results were obtained after 1 minute of exposure with catalyzed signal amplification and after 6 minutes with other detection systems. Regarding cyclin D1 expression in mantle cell lymphoma cases, 17 (85%) were weakly positive and 3 (15%), moderately positive with labeled streptavidin biotin, whereas 15 (75%) were weakly positive and 5 (25%) moderately positive with EnVision+. In contrast, all 20 mantle cell lymphoma cases were strongly cyclin D1 positive with catalyzed signal amplification. No evidence of cyclin D1 immunostaining was obtained in any of the small lymphocytic lymphoma and follicular center cell lymphoma instances with any of the three methods used. In conclusion, catalyzed signal amplification methods provide a very useful tool for cyclin D1 demonstration in cases in which other immunohistochemical techniques yield inconclusive results.