Ovarian cysts often have no symptoms or problems, but some types can cause discomfort that can range from mild to severe. (Image credit: Kinga Krzeminska via Getty Images)
Ovarian cysts are quite common among menstruating people: an estimated 10–30% of women (and possibly more) will have at least one cyst during their lifetime.
These fluid-filled growths appear in or on the surface of the ovaries, small organs located on either side of the uterus that produce the hormones estrogen and progesterone and release eggs each month during the menstrual cycle.
Most ovarian cysts develop as a result of a normal menstrual cycle and do not cause any problems. However, not all ovarian cysts are the same. Some are harmless and painless, while others can be extremely painful or even cancerous. The type of cyst and any complications that may occur will determine the symptoms and treatment needed.
Learn more about ovarian cysts, what causes them, and whether they need treatment.
What are ovarian cysts?
“An ovarian cyst is a fluid-filled sac that forms on or inside the ovary,” Adam Taylor, a professor of anatomy at Lancaster University in the U.K., told Live Science in an email. “They can often be quite large, and in many cases are comparable in size to the ovary itself.” The ovary is about 1.2 by 0.8 by 0.4 inches (3 by 2 by 1 centimeter), while most ovarian cysts are between 0.4 and 1.2 inches (1 and 3 centimeters) in diameter.
Ovarian cysts can be divided into two main categories: functional and pathological. Functional cysts, also known as “simple cysts,” are the most common because they can form as part of the normal menstrual cycle. They are called “functional” because they are usually due to the normal functioning of the ovaries and are not cancerous or disease-related. However, they can cause significant symptoms, especially if they are large.
There are two types of functional cysts: follicular cysts and corpus luteum cysts, depending on the tissue in which they form.
Unlike functional ovarian cysts, other types of ovarian cysts are less common. They are not related to the menstrual cycle and are known as pathological or complex cysts. They are usually caused by abnormal cell growth, which can be caused by a variety of factors, including hormonal imbalances, pelvic infections, or conditions such as endometriosis.
(In some cases, hormonal imbalances can also contribute to the formation of functional cysts, as they can affect ovulation.)
Pathological cysts are usually benign or noncancerous. These include dermoid cysts, cystadenomas, endometriomas, and small cysts associated with the hormonal condition polycystic ovary syndrome (PCOS).
However, a small percentage of abnormal cysts—less than 1%—are malignant or cancerous. These ovarian cancer cysts are masses of cancer cells and are most common after menopause.
Why do ovarian cysts form and who is at risk for them?
Functional ovarian cysts are often part of the normal menstrual cycle, so “about 1 in 10 women will have an ovarian cyst at some point in their life,” says Taylor. “Once you’ve had one, you’re more likely to get another.”
Functional cysts can form from follicles or the corpus luteum. To understand how and when these cysts form, let's first look at the phases of the menstrual cycle:
Each ovary contains egg follicles, small sacs containing immature eggs (oocytes). At the beginning of each menstrual cycle, several of these follicles begin to mature and develop. One of the mature follicles eventually ruptures and releases an egg during ovulation. The empty follicle then transforms into a temporary
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