- An ovarian cyst is a small sac filled with fluid, located in the ovary. Approximately 95 percent of ovarian cysts are benign, or non-cancerous. While some benign cysts may be due to endocrine disorders or other conditions, any ovarian follicle over 2 cm can also be called an ovarian cyst. Most ovarian cysts are so-called "functional cysts." Functional cysts are generally harmless and often do not require treatment.
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FolliculogenesisFunctional ovarian cycts can occur as part of the process of folliculogenesis and ovulation. At any given time, a post-pubertal woman has ovarian follicles at all stages of development in her ovaries. There are three types of functional cysts.
Follicular Cyst: This is a mature ovarian follicle that is not released during ovulation, or collapses in on itself prior to ovulation. While these cysts can grow as large as 2 1/3 inches in diameter and can cause pain if they rupture, they are generally harmless and will disappear on their own in a few months.
Corpus Luteum Cyst: At the time of ovulation, the ovarian follicle releases the mature egg. The follicle then becomes known as the corpus luteum. Normally, the corpus luteum breaks down and is reabsorbed by the body, but it may fill with blood or fluid and stay in the ovary. The corpus luteum cyst does not generally cause symptoms.
Hemorrhagic Cyst: At some point during folliculogenesis, a blood vessel in the ovarian follicle may burst, causing blood to leak into the follicle. Generally, the bleeding will subside on its own, but if it does not, blood can leak into the ovary and cause it to enlarge. This can cause extreme pain. Should the cyst rupture, blood can leak into the abdominal cavity. Hemorrhagic cysts occasionally require surgery. - Endometriosis is a condition in which the tissue that lines the uterus (the endometrium) grows outside of the womb. The primary symptom is severe, recurring abdominal and pelvic pain. An endometrial cyst occurs when a small amount of endometrial tissue grows inside the ovary. The cyst might grow for months or even years before rupturing. This can lead to infertility. About 5 to 10 percent of women have endometriosis, and are therefore at risk for endometrial cysts.
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An ultrasound image of a polycystic ovaryPolycystic ovarian syndrome, or PCOS, is an endocrine disorder in which several ovarian follicles develop to about half the size of a preovulatory follicle, but then cease to mature. If an ultrasound detects 12 or more of these follicles, the ovary is said to be polycystic. It should be noted that a woman can have a polycystic-appearing ovary without having the endocrine problems that connote PCOS.
