WT1 and malignant pleural mesothelioma: More importantly, no cytoplasmic WT1 immunoreactivity was seen in any of the tumors evaluated by using clone WT49, whereas clone 6F-H2 showed WT1 cytoplasmic staining in 7 (17.5%) malignant pleural mesotheliomas, 17 (30.1%) lung carcinomas, and 5 (50.0%) synovial sarcomas [161].