Endometrial biopsy is a procedure that exams the endometrium (the inside lining of the uterus) for abnormalities or signs of cancer. The biopsy is done by taking a tissue sample of the endometrium and checking it under a microscope. A speculum is inserted in the vagina, followed by a small plastic tube that suctions a sample of the lining off. Anesthesia may be used, but the procedure is usually painless. This test is usually performed to determine the cause of abnormal menstrual periods, bleeding after menopause or to screen for endometrial cancer.