WFDC2 (WAP four-disulfide core domain protein 2), also known as human epididymal secretory protein E4 (HE4), is a small secreted broad range protease inhibitor. WFDC2 is a diagnostic marker in ovarian, endometrial and other cancers, and can be detected in patient serum. WFDC2 expression promotes tumor growth, contributes to metastasis and epithelial mesenchymal transition (EMT), and regulates angiogenesis and immunogenic signaling in the tumor microenvironment.