Cell proliferation rate and telomerase activity in the differential diagnosis between benign and malignant mesothelial proliferations.

Aims: The differential diagnosis of malignant mesothelioma (MM) from benign mesothelial lesions (BML) based on histopathological criteria is sometimes not satisfying and causes diagnostic problems for histopathologists. We aimed to investigate whether the immunohistochemically determined cell proliferation rate and telomerase activity, using Ki-67 and human telomerase reverse transcriptase (hTERT) immunohistochemistry, respectively, are useful in the differential diagnosis of MM from BML.

Methods: Sixty-six cases of MM (33 epithelioid, 30 biphasic and 3 sarcomatoid) and 22 cases of BML (15 reactive mesothelial proliferations and 7 fibrous pleuritis/pericarditis) were included in this study. We evaluated the proliferative activity by Ki-67 and telomerase activity by hTERT immunohistochemistries for each case.

Results: The mean value of the Ki-67 proliferation index (PI) in MMs was significantly higher than that of BMLs. Biphasic MMs have higher a Ki-67 PI than epithelioid and sarcomatoid types. Ki-67 immunohistochemistry has a sensitivity of 74%, specificity of 86% and positive predictive value of 94% in detecting MM. hTERT immunohistochemistry detected MM with sensitivity and specificity of 68%.

Conclusion: As a result, being cheap and simple methods, Ki-67 and hTERT immunohistochemistries can be used in differentiating malignant and benign mesothelial lesions in routine formalin-fixed, paraffin-embedded material.