Abstract

Introduction: the differentiation of mesothelioma from reactive mesothelial hyperplasia can be challenging, especially in effusion cytology or when tissue biopsies are not feasible, making immunohistochemical studies a substantial tool in establishing the appropriate diagnosis.

Aim of the work: the current study aimed to evaluate immunohistochemical expression of MTAP as well as EMA in epithelioid pleural mesothelioma (EPM) and reactive mesothelial hyperplasia (RMH) in both cell block preparations and tissue specimens, and to compare the diagnostic utility of MTAP and EMA in mesothelioma.

Material and methods: after confirmation of the mesothelial lineage, immunohistochemical expression of MTAP and EMA antibodies in both tissue biopsies and cell blocks; obtained from 30 cases of EPM and 30 cases of RMH; was evaluated.

Results: MTAP differentiated EPM from RMH with 63.3% sensitivity (64.7% for tissue biopsies and 61.5% for cell blocks) and 100% specificity (100% for both tissue biopsies and cell blocks); the optimal cut-off value for MTAP expression that could best distinguish EPM from RMH was 52.5%. On the other hand, EMA differentiated EPM from RMH with 93.3% sensitivity (88.2% for tissue biopsies and 100% for cell blocks) and 66.7% specificity (58.3% for tissue biopsies and 72.2% for cell blocks).

Conclusion: MTAP is a highly specific marker for distinguishing EPM from RMH, whereas EMA showed a significant sensitivity for differentiation of EPM and RMH. Moreover, cell block preparations could be a reliable surrogate for tissue biopsies to differentiate mesothelial lesions.