Mesothelin, a glycosylphosphatidylinositol (GPI)-anchored cell surface glycoprotein. Normally, its expression is largely restricted to mesothelial cells lining body cavities. In pathology, mesothelin is highly overexpressed in a range of aggressive cancers, including malignant pleural mesothelioma (≥90%), pancreatic adenocarcinoma (~70%), and serous ovarian carcinoma. This tumor-specific overexpression, combined with its cell surface localization and ability to be internalized upon antibody binding, makes it an ideal target for ADC therapy.