Non-cancerous ovarian formations include cysts (mainly functional) and benign tumors. Most non-cancerous cysts and tumors do not cause any symptoms, but some cause pain or a feeling of heaviness in the pelvis. Ovarian cysts are fluid-filled sacs that form in or on the ovary. Such cysts are relatively common. Most are non-cancerous (benign) growths and disappear on their own. Cancerous cysts are more likely to occur in women over the age of 40. Functional cysts form from the fluid-filled cavities (follicles) in the ovaries. Each follicle contains one egg. Normally, during each menstrual cycle, a follicle releases an egg and the follicle disappears after the egg is released. However, if the egg is not released, the follicle may continue to enlarge, forming a larger cyst. About a third of menstruating women have cysts. Functional cysts rarely develop after menopause. Functional cysts can be of two types: Follicular cysts. These cysts form when the egg develops in the follicle. Cysts of the corpus luteum. These cysts develop from the structure that forms after the follicle ruptures and the egg is released. This structure is called the corpus luteum. Corpus luteum cysts can bleed, leading to rupture of the ovary. If the cyst ruptures, fluids leak into the abdominal cavity and may present with severe pain. Most functional cysts are smaller in size. Functional cysts usually disappear on their own. Benign ovarian tumors usually grow slowly and rarely become malignant. The most common include: Benign cystic teratomas (dermoid cysts). These tumors usually develop from the three germ cell layers. All organs are formed from these tissues. Thus, teratomas can contain tissues from other structures, such as nerves, glands, hair, skin. Fibroids. These formations are solid masses composed of connective tissue. Fibroids are slow-growing and usually measure about 7 centimeters in diameter. They usually affect only one ovary. Cystadenomas. These fluid-filled cysts develop from the surface of the ovary and contain some ovarian glandular tissue. Most functional cysts and non-cancerous ovarian tumors do not cause any symptoms. Sometimes affected women report dull pain in the pelvic area or pain during intercourse. Some cysts produce hormones that affect the menstrual cycle. As a result, periods may be irregular or heavier than normal. Spotting may occur between periods. In postmenopausal women, such cysts can cause vaginal bleeding. If corpus luteum cysts bleed, they may cause pain or tenderness in the pelvic area. Sometimes, sudden, severe abdominal pain occurs because a large cyst or mass causes the ovary to twist (adnexal torsion).Fluid accumulation in the abdomen (ascites) can occur with fibroids and ovarian cancer. Ascites can cause a feeling of pressure or heaviness in the abdomen. References: https://www.msdmanuals.com/home/women-s-health-issues/miscellaneous-gynecologic-abnormalities/noncancerous-ovarian-growths