Human Epididymis Protein 4 is a protein that is produced by most, but not all, epithelial ovarian cancer cells. This makes the test useful as a tumor marker in specific circumstances. The HE4 test measures the amount of human epididymis protein 4 in the blood. Significantly elevated concentrations of HE4 are frequently present in the blood of a woman who has epithelial ovarian cancer. When HE4 is increased, the HE4 test may be used to monitor the effectiveness of treatment and/or for recurrence of the cancer. However, HE4 is not recommended as a screening test for asymptomatic women because it is non-specific. Small quantities of HE4 are produced by normal tissues throughout the body and mild elevations may be seen with a variety of non-cancerous conditions. HE4 is not recommended as a screening test for asymptomatic women because it is non-specific. Small quantities of HE4 are produced by normal tissues throughout the body and mild elevations may be seen with a variety of non-cancerous conditions.