The Role of Immunohistochemistry Studies in Distinguishing Malignant Mesothelioma from Metastatic Lung Carcinoma in Malignant Pleural Effusion

Background and Objective: Early diagnosis of malignant pleural mesothelioma (MPM) is the key point of its treatment. The main problem is the precise diagnosis of mesothelioma and its differentiation from metastatic lung adenocarcinoma. Mesothelioma exhibits complex immunohistochemical characteristics. The aim of this study was to study hybrid immunohistochemistry in the differential diagnosis of primary malignant pleural effusion from metastatic pulmonary cancers. Material and Methods: Twenty tissue samples in paraffin blocks from the pathology department of Imam Reza Hospital in Tabriz whose pathology reports cited mesothelioma or metastatic lung adenocarcinomas, were included in the studies. These tissues were deemed appropriate for IHC in terms of tissue quality and quantity. They were studied and evaluated for pathological markers.  Results: In patients with adenocarcinoma CK7 in 100% of patients (13 patients), TTF1 in 61.5% of patients (8 patients) and CEA in 53.8% of patients (7 patients) were positive, but HBME1 and Calretinin were negative for all patients. In patients with mesothelioma, HBME1 and Calretinin were positive in 100% of patients (7 patients) and TTF1, CEA and CK7 were negative. Conclusion: The results of this study showed that CEA, CK7, TTF1, Calretinin and HBME1 are suitable criteria for differentiating between metastatic lung adenocarcinoma and mesothelioma, and can differentiate the mesothelioma and adenocarcinoma with high accuracy.