An endometrial biopsy is a 10-minute, in-office gynecologic procedure in which a small tissue sample is collected from the lining of the uterus for examination under a microscope. It is usually recommended when a woman experiences abnormal vaginal bleeding or when an abnormality is detected following a routine Pap test. The sample is collected using a thin, plastic device called a pipelle, which is placed in the uterus and creates a small amount of suction in order to gather the cells needed for examination. Alternatively, an electronic suction device or irrigation technique may be employed for this purpose. In addition to helping detect or rule out uterine cancer, an endometrial biopsy can help detect any imbalance in the hormone levels that affect the endometrium (uterine lining).