There are many efforts underway to target mesothelin (MSLN), a cell surface protein overexpressed by epithelioid mesothelioma, non-small cell lung cancer (NSCLC), gynecologic cancers (ovarian, endometrial, cervical, vulvar), pancreatic cancer, head and neck cancer, and esophageal cancer, while maintaining limited expression in normal tissues1–4. Here, MSLN is linked to malignant epithelioid mesothelioma.