by Emily Goebel, MD FRCPC
January 12, 2023
Endometrial hyperplasia without atypia is a non-cancerous condition associated with an abnormally thick endometrium. Another name for endometrial hyperplasia without atypia is benign endometrial hyperplasia.
Endometrial hyperplasia without atypia is associated with a very small risk of developing a type of endometrial cancer called endometrioid carcinoma over time. The risk is increased in women with high levels of estrogen.
Symptoms of endometrial hyperplasia without atypia include abnormal uterine bleeding, such as heavy menstrual bleeding, bleeding between menstrual periods, or postmenopausal bleeding.
Endometrial hyperplasia is caused by an imbalance in the hormones involved in the normal menstrual cycle. During the menstrual cycle, the endometrium cycles through a proliferative phase (growth phase) and secretory phase in response to hormones (estrogen and progesterone) made and released by the ovaries.
In a normal menstrual cycle, the endometrium grows thicker under the influence of estrogen during the proliferative phase. This is followed by ovulation where a mature egg is released from the ovary, pushed down the fallopian tube, and made available to be fertilized.
After ovulation, the endometrium enters the secretory phase under the influence of progesterone. If fertilization does not occur, the endometrium breaks down, which leads to the discharge of blood and endometrial tissue through the vagina (menstruation, menstrual period, menstrual flow).
Some women experience an imbalance in the hormones that control the growth of the endometrium, resulting in high levels of estrogen and low levels of progesterone. When there is too much estrogen and not enough progesterone, the endometrium continues to grow and becomes abnormally thick. This change is called endometrial hyperplasia.
Some common situations that can result in increased or prolonged estrogen exposure include polycystic ovary syndrome, obesity, estrogen-only birth control pills, and tamoxifen treatment. Women nearing menopause (perimenopause) may also experience prolonged estrogen exposure.
In patients with abnormal uterine bleeding, the endometrium is sampled by endometrial biopsy or endometrial (uterine) curetting (scrapings of the endometrium with a spoon-shaped instrument). The tissue sample is then examined by your pathologist under the microscope.
When viewed under the microscope, the abnormally thick endometrium can show a variety of changes that include both non-cancerous conditions and pre-cancerous conditions that can lead to cancer over time. In cases of endometrial hyperplasia without atypia, your pathologist will see crowded endometrial glands that are irregular in size and shape. However, the epithelial cells that line the inside of the glands will not look atypical (abnormal).
Treatment options for this condition include oral progestins and intrauterine devices (IUDs). Your doctor will probably also suggest a follow-up endometrial biopsy. For more information about treatment options, please speak to your doctor.