Ovaries produce the hormone estrogen and the egg that is released monthly – a process called ovulation – during a woman’s reproductive years. PCOS is a condition of the female reproductive system that causes a bunch of small cysts, which are tiny sacs of fluid, to form on the ovaries. Women with PCOS typically do not ovulate and have abnormally high levels of androgen hormones, often called “male” hormones. While most of the time these cysts will be benign (non-cancerous), they may still require treatment or removal.

Women with PCOS also have increased levels of estrogen and abnormally low levels of progesterone. Hormone levels play a big role when it comes to cancer risk — particularly types of uterine cancer like endometrial cancer.

What can happen if a cyst is left untreated? Some cysts are cancerous and early treatment is vital. If left untreated, benign cysts can cause serious complications including Infection – the cyst fills with bacteria and pus, and becomes an abscess. If the abscess bursts inside the body, there is a risk of blood poisoning.

Women with PCOS and other factors that increase estrogen levels including obesity, diabetes, or taking medications are more likely to develop endometrial cancer than those without these factors. The abnormal amounts of estrogen are particularly risky when not balanced by sufficient progesterone levels in the blood. This is why post-menopausal women who have not had a hysterectomy and who need treatment for severe menopausal symptoms will be prescribed both estrogen and progesterone, instead of estrogen alone.

Do ovarian cysts increase the risk of ovarian cancer?

Ovarian cysts are very common and can affect women of any age. They are more frequent in women of childbearing age because they are linked to ovulation.

Ovarian cancer is increased 2- to 3-fold in women with PCOS. This risk is greatest in women who have not been on oral contraceptives. Because of the known protective effect of oral contraceptives on ovarian and endometrial cancer risk, use of oral contraceptives should be strongly considered as a preventative therapy.

It is unclear if women with PCOS have an increased risk of breast cancer, partially because other factors like obesity and nulliparity are confounding variables. Because an association between PCOS and breast cancer is plausible, it is imperative to be vigilant about breast disease in the follow-up care of all women with PCOS.