Gene expression analysis of the catalytic subunit of human telomerase (hEST2) in the differential diagnosis of serous effusions

Diagnostic accuracy in effusion cytology based on morphologic examination i s not always satisfactory. Therefore, various diagnostic adjuncts such as i mmunocytochemistry or deoxyribonucleic acid cytometry are employed in this diagnostic field. Recently, demonstration of telomerase activity has been p roposed as a possible marker for malignancy. In this study a seminested rev erse transcription-polymerase chain reaction (RT-PCR) strategy for expressi on analysis of the catalytic subunit of human telomerase (hEST2) was used i n 58 serous effusions. RT-PCR results correlated with cytologic diagnoses i n 14 of 17 malignant effusions. In eight effusions cytologically suspicious for malignancy, PCR results were in accordance with the clinical follow-up . However, hEST2 RT-PCR was also positive in six of 15 cytologically benign effusions that consisted predominantly of inflammatory and mesothelial cel ls. Using the telomeric repeat amplification protocol, it could be demonstr ated that cultured, proliferating benign mesothelial cells may present a we ak telomerase activity, as is known in other benign cells including activat ed lymphocytes. In conclusion, the simple and rapid method of hEST2 RT-PCR serves to support the cytologic diagnosis of malignancy, but false-positive PCR results resulting from activated lymphocytes and proliferating mesothe lial cells must be considered.