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 is not always satisfactory. Therefore, various diagnostic adjuncts such as immunocytochemistry or deoxyribonucleic acid cytometry are employed in this diagnostic field. Recently, demonstration of telomerase activity has been proposed as a possible marker for malignancy. In this study a seminested reverse transcription-polymerase chain reaction (RT-PCR) strategy for expression analysis of the catalytic subunit of human telomerase (hEST2) was used in 58 serous effusions. RT-PCR results correlated with cytologic diagnoses in 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 cells. Using the telomeric repeat amplification protocol, it could be demonstrated that cultured, proliferating benign mesothelial cells may present a weak telomerase activity, as is known in other benign cells including activated 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 mesothelial cells must be considered.