In situ hybridization and reverse transcription-polymerase chain reaction for cyclin D1 mRNA in the diagnosis of mantle cell lymphoma in paraffin-embedded tissues

Mantle cell lymphoma (MCL) is characterized by the chromosomal translocatio n t(11;14), which involves rearrangement of the bcl-1 proto-oncogene to the immunoglobulin heavy chain gene and results in overexpression of cyclin D1 mRNA. In this study, we evaluated the diagnostic relevance of three method s that may be helpful in the diagnosis of MCL: in situ hybridization (ISH) and a stringent reverse transcriptase-polymerase chain reaction (RT-PCR) pr otocol for cyclin D1 mRNA, and immunohistochemistry for cyclin D1 protein. The study group included 37 paraffin-embedded specimens (25 from lymph node s and 12 from extranodal tissues) from 30 patients. MCL diagnosis was perfo rmed according to the Revised European-American Classification of Lymphoid Neoplasms. Twenty-nine patients with non-MCL lymphoproliferative disorders comprised the control group. Biotin-labeled ISH was performed in 28 cases o f MCL, 24 (86%) of which were found to be positive. As shown by ISH in extr anodal tissues, cyclin D1 mRNA was present not only in neoplastic lymphoid cells, but in other cell types as well. For this reason, RT-PCR results wer e considered reliable for MCL diagnosis only on informative material (from tissues that do not normally express cyclin DI); this method was evaluated as positive in 16 of 18 (89%) MCL cases. Cyclin DI immunopositivity was pre sent in 20 of 29 (69%) MCL cases. No members of the control group were foun d to express cyclin DL mRNA by either ISH or RT-PCR under the stringent con ditions used. In conclusion stringent RT-PCR for cyclin D1 expression can b e helpful in MCL diagnosis in paraffin-embedded material from lymph nodes. ISH is a sensitive method for cyclin DI mRNA detection; its sensitivity is superior to that of cyclin D1 immunohistochemistry and similar to that of t he stringent RT-PCR used. ISH is very specific as well, clearly more specif ic than RT-PCR, because it allows the correlation of molecular findings wit h morphology. This method can be applied on all types of paraffin-embedded tissues and provides an accurate tool for MCL diagnosis.