Atypical endometrial hyperplasia

Having atypical endometrial hyperplasia* is associated with an increased risk of endometrial cancer. Atypical endometrial hyperplasia may go on to develop into endometrial cancer. Studies show that 28% of women who have atypical endometrial hyperplasia go on to develop endometrial cancer. In some women, atypical endometrial hyperplasia may exist alongside endometrial cancer. Around 42% of women with atypical endometrial hyperplasia also have endometrial cancer at the time of hysterectomy.

Endometrial hyperplasia is thought to be caused by continuous exposure to the female hormone oestrogen. The hormonal risk factors that increase the risk of endometrial cancer are also thought to increase the risk of endometrial hyperplasia.

*Endometrial hyperplasia is a condition in which the cells in the lining of the uterus grow faster than normal. There are two types of endometrial hyperplasia: typical and atypical. Atypical endometrial hyperplasia is thought to be a precancerous condition that can develop into endometrial cancer. Typical endometrial hyperplasia is less likely to progress to endometrial cancer.

Endometrial polyps

There is convincing evidence of a small association between endometrial polyps* and risk of endometrial cancer. Studies suggest that around 2–3% of endometrial polyps can become malignant (develop into cancer). The risk of endometrial polyps becoming malignant is higher if the polyps are causing bleeding, and if polyps occur in women who have reached menopause. 

Endometrial polyps are thought to be caused by overstimulation of endometrial glands by the female hormone oestrogen (or chemicals with similar effects to oestrogen).

*Endometrial polyps are small growths or projections of endometrial tissue from the lining of the uterus. Polyps may cause bleeding or may exist without causing symptoms. Most polyps shrink over time.