There are several types of ovarian cysts, ranging from harmless fluid-filled sacs that form during a normal menstrual cycle to growths that contain tissue, blood, or mucus. Most ovarian cysts are benign and resolve without treatment, but some types persist, grow large, or cause complications. Understanding which kind you’re dealing with helps make sense of what your doctor tells you and what to expect next.
Functional Cysts
Functional cysts are by far the most common type. They form as a normal part of ovulation and are not a sign of disease. There are two subtypes, and both typically disappear on their own.
Follicular Cysts
Each month, an egg grows inside a small sac called a follicle. Normally, the follicle breaks open to release the egg. When it doesn’t rupture, the follicle keeps filling with fluid and becomes a cyst. Follicular cysts are usually small and painless, and most resolve by your next menstrual cycle without any treatment.
Corpus Luteum Cysts
After a follicle releases its egg, the empty sac normally shrinks and helps produce hormones for the rest of the cycle. Sometimes, instead of breaking down, it seals shut and fills with fluid. The resulting corpus luteum cyst can range from just under 2 centimeters to about 5 centimeters. If you’re not pregnant, these cysts typically go away within a few weeks. During pregnancy, they usually resolve by the second trimester.
Functional cysts can occasionally rupture, and that rupture is often part of a normal cycle. Many women never know it happened. When a rupture does cause symptoms, sharp lower abdominal pain is the hallmark, sometimes with nausea or vomiting. Sudden, severe pain with dizziness, vision changes, or a racing heartbeat can signal significant internal bleeding and needs emergency attention.
Dermoid Cysts
Dermoid cysts (also called mature cystic teratomas) are one of the more unusual types. They develop from cells present since birth that have the ability to become many different tissue types. That means a dermoid cyst can contain skin, hair, fat, and even fragments of bone or teeth. Sebaceous (oily) material is found in almost every case, giving these cysts a dense, waxy interior.
About 38% of dermoid cysts contain only skin and nerve tissue, while another 30% contain skin and structures like hair follicles or sweat glands. The rest hold a wider mix of fully formed tissues. Dermoid cysts grow slowly, often over years, and tend to show up in women of reproductive age. They don’t resolve on their own the way functional cysts do. Surgical removal is the standard approach, especially once a dermoid reaches a size that raises the risk of complications like torsion, where the ovary twists on itself.
Endometriomas
Endometriomas form when tissue similar to the uterine lining grows on or inside an ovary, a process tied directly to endometriosis. These cysts fill with old blood and endometrial debris, creating a thick, dark brown fluid that gives them the nickname “chocolate cysts.”
On ultrasound, endometriomas have a distinctive ground-glass appearance, a hazy, uniform pattern caused by the old blood inside. They typically show no internal blood flow on Doppler imaging, which helps distinguish them from other types of cysts. Some appear as simple single-chamber cysts, while others have multiple compartments or solid-looking areas.
Endometriomas don’t go away on their own. They can cause chronic pelvic pain, painful periods, and pain during sex. They’re also associated with reduced fertility, since the inflammatory environment they create can damage surrounding ovarian tissue. Treatment depends on size, symptoms, and whether you’re trying to conceive, but often involves surgery, hormonal therapy, or both.
Cystadenomas
Cystadenomas are benign growths that develop on the outer surface of the ovary. Unlike functional cysts, they arise from ovarian tissue itself rather than from the ovulation process. There are two main subtypes.
Serous cystadenomas are filled with thin, watery fluid. They can have one chamber or several, and their size ranges from 1 centimeter to over 30 centimeters, with an average around 10 centimeters. Mucinous cystadenomas contain thicker, gel-like fluid and tend to have multiple compartments. They cover a similar size range, also averaging about 10 centimeters, but the largest ones can grow dramatically and fill a significant portion of the abdomen.
Both types are benign, but they can recur after surgical removal if any cyst tissue is left behind. Because they can grow quite large, they’re more likely than smaller cysts to cause noticeable pressure, bloating, or a feeling of fullness in the pelvis. Large cystadenomas are also candidates for torsion.
Polycystic Ovaries vs. Single Cysts
The word “cyst” in polycystic ovary syndrome (PCOS) can be misleading. PCOS doesn’t involve the types of cysts described above. Instead, it’s characterized by many small, immature follicles, typically 12 or more per ovary, each measuring 2 to 9 millimeters. These follicles are often arranged around the edge of an enlarged ovary (10 cubic centimeters or more in volume) and represent eggs that started developing but never matured enough to ovulate.
A solitary ovarian cyst is usually a single, distinct fluid-filled structure that developed from one cycle or one growth event. The small follicles seen in PCOS are a pattern reflecting a hormonal imbalance, not a collection of individual cysts in the clinical sense. The distinction matters because the causes, symptoms, and management are completely different.
When Size Becomes a Risk Factor
Most ovarian cysts, regardless of type, cause no symptoms when they’re small. As they grow, you may notice dull pelvic pressure, bloating, or a sense of heaviness on one side. Pain during sex or difficulty emptying your bladder can occur when a cyst presses on nearby structures.
The more serious concern with larger cysts is ovarian torsion, where the weight of the cyst causes the ovary to twist and cut off its own blood supply. The risk increases significantly once a cyst or mass reaches 5 centimeters (about 2 inches) across. Torsion causes sudden, intense pain, often with nausea and vomiting, and requires emergency surgery to save the ovary.
Rupture is the other acute complication. There’s no reliable warning sign that a cyst is about to burst. When it does, the pain can be severe and may come with fever (suggesting infection), nausea from fluid irritating the abdominal lining, or dizziness if there’s significant bleeding. Mild ruptures often resolve with rest and pain management. Severe cases with heavy bleeding need intervention.