Optimized cyclin D1 immunoperoxidase staining in mantle cell lymphoma

Mantle cell lymphoma (MCL) has a worse prognosis than MALT lymphoma (MALTL) . Distinction between MCL and MALTL on purely morphologic grounds can be di fficult. Cyclin D1 (PRAD1/bcl1) is overexpressed in MCL as a result of a t( 11:14) gene rearrangement, which leads to overexpression of cyclin D1 mRNA and protein. The immunohistochemical detection of cyclin D1 in MCL has been reported by several authors to be highly specific with sensitivity ranging from 70%-100%, but diagnostic laboratories have reported difficulty in fin ding a reliable method for cyclin D1 immunostaining. The aim of this study was to evaluate and optimize a method for detection of cyclin D1 by paraffi n section immunoperoxidase staining. Sections of routinely processed tissue from five MCL and one splenic marginal zone lymphoma (MZL) were immunostai ned using a mixture of two primary monoclonal antibodies and a standard avi din-streptavidin method. Antigen retrieval was performed using 1) steam hea t in citrate buffer, 2) as in "1" followed by sonication for one minute, an d 3) as in "2" followed by enzymatic digestion. All the above were repeated , with the additional use of catalyzed signal amplification (CSA). Later, s ections of the same cases, plus three MALTL were immunostained as in"2". St eam heat antigen retrieval alone produced the best results. All MCL showed positive nuclear staining while the MZL and all MALTL were negative. Sonica tion did not enhance staining noticeably, whereas enzymatic digestion produ ced cytoplasmic staining. CSA increased background staining with no signifi cant gain in nuclear stain intensity. We conclude that cyclin D1 immunostai ning of formalin-fixed, paraffin-embedded tissue can be reliably achieved b y heat induces antigen retrieval and a cocktail of two monoclonal antibodie s.