Immunohistochemical Differentiation between Reactive and Malignant Mesothelial Proliferations in Pleural Effusion

Abstract
Background: The differentiation between benign and malignant mesothelial cells in pleural effusion in some cases can be a challenge. In the current study, we investigated the value of immunohistochemistry (IHC) in making that differ-entiation.
Aim of Study: This study aims to examine the value of IHC expression of desmin, EMA, GLUT-1, p53, Ki67, and BAP1 in discrimination between benign and malignant mes-othelial proliferation in pleural effusions and compare their results regarding sensitivity and specificity.
Material and Methods: Pleural fluids from 30 cases diagnosed as malignant meothelioma (MM) epitheloid type and 20 cases diagnosed as reactive mesothelial hyperplasia (RMH) were selected, and stained with immunohistochemical stains included BAP-1, desmin, epithelial membrane antigen (EMA), glucose-transport protein 1 (GLUTÅ]1), Ki67, and p53.
Results: BAP-1 was negative in 5% (1 of 20) cases of reactive MH and in 63.3% (19 of 30) of MM cases (p<.005). GLUTÅ] 1 was positive in 15% (3 of 20) of benign and 70% (21 of 30) of malignant cases (p<.005). Desmin was positive in 80% (16 of 20) cases of reactive MH and in 10% (3 of 30) of MM cases (p<.001). EMA was positive in 10% (2 of 20) of benign and 96.7% (29 of 30) of malignant cases (p<.001). P53 showed strong nuclear positivity in 5% (1 of 20) of benign and 53.3% (16 of 30) of malignant cases (p<.001). Ki67 showed strong nuclear positivity in >40% of mesothelial cells in 10% (2 of 20) of benign and 16.7% (5 of 30) of malignant cases (p=0.40). EMA negativity and desmin positivity were found in 75% (15 of 20) of reactive MH cases and 3.3% (one of 30) of MM cases. EMA positivity and desmin negativity were found in 5% (1 of 20) of reactive MH cases and 90% (27 of 30) of MM cases (p<.001). Positivity for both of Desmin and BAP-1 was detected in 80% (16 of 20) of RMH cases. The combination of Desmin and BAP-1 negativity was detected in 60% (16 of 30) of MM cases (p-value p<.001).
Conclusions: Cases showed positivity for EMA and neg-ativity for desmin strongly favors malignant mesothelioma. On the contrary, cases showed negative EMA and positive desmin strongly favors Reactive mesothelial hyperplasia. also the combination of Desmin and Bap-1 postivity favors diagnosis of RMH, and the combination of Desmin and BAP-1 negativity favors the diagnosis of MM. Similarly, cases showed strong membranous expression of GLUT-1 and/or strong nuclear expression of p53 strongly favors diagnosis of malignant mesothelioma. Proliferative index showed detected by Ki67 showed no significant difference between reactive and malignant cases.