MUC4 and malignant epithelioid mesothelioma: In this study, We found MUC4 expression in 50/60 (83.3%) cases of lung adenocarcinoma, 50/56 (89.3%) cases of squamous cell carcinoma, and none (0%) of epithelioid mesothelioma. Kwon et al. 14  and Llinares et al. 21  previously reported the diagnostic value of MUC4 expression in distinguishing epithelioid mesothelioma and lung adenocarcinoma.