Ovarian cysts
Ovarian cysts are fluid-filled sacs in the ovary. They are common and usually form during ovulation. Ovulation happens when the ovary releases an egg each month. Many women with ovarian cysts don't have symptoms. The cysts are usually harmless.
The most common types of ovarian cysts (called functional cysts) form during the menstrual cycle. They are usually benign (not cancerous).
The two most common types of cysts are:
follicle cysts. In a normal menstrual cycle, an ovary releases an egg each month. The egg grows inside a tiny sac called a follicle. When the egg matures, the follicle breaks open to release the egg. follicle cysts form when the follicle doesn't break open to release the egg. This causes the follicle to continue growing into a cyst. follicle cysts often have no symptoms and go away in one to three months.
Corpus luteum cysts. Once the follicle breaks open and releases the egg, the empty follicle sac shrinks into a mass of cells called corpus luteum. Corpus luteum makes hormones to prepare for the next egg for the next menstrual cycle. Corpus luteum cysts form if the sac doesn't shrink. Instead, the sac reseals itself after the egg is released, and then fluid builds up inside. Most corpus luteum cysts go away after a few weeks. But, they can grow to almost four inches wide. They also may bleed or twist the ovary and cause pain. Some medicines used to cause ovulation can raise the risk of getting these cysts.
Other types of benign ovarian cysts are less common:

Endometriomas are caused by endometriosis. Endometriosis happens when the lining of the uterus (womb) grows outside of the uterus.
Dermoids come from cells present from birth and do not usually cause symptoms.
Cystadenomas are filled with watery fluid and can sometimes grow large.
In some women, the ovaries make many small cysts. This is called polycystic ovary syndrome (PCOS). PCOS can cause problems with the ovaries and with getting pregnant.

Malignant (cancerous) cysts are rare. They are more common in older women. Cancerous cysts are ovarian cancer. For this reason, ovarian cysts should be checked by your doctor. Most ovarian cysts are not cancerous.

Most ovarian cysts are small and don't cause symptoms.

If a cyst does cause symptoms, you may have pressure, bloating, swelling, or pain in the lower abdomen on the side of the cyst. This pain may be sharp or dull and may come and go.

If a cyst ruptures, it can cause sudden, severe pain.

If a cyst causes twisting of an ovary, you may have pain along with nausea and vomiting.

Less common symptoms include:

Pelvic pain
Dull ache in the lower back and thighs
Problems emptying the bladder or bowel completely
Pain during sex
Unexplained weight gain
Pain during your period
Unusual (not normal) vaginal bleeding
Breast tenderness
Needing to urinate more often

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