Four types of benign ovarian cysts are most commonly encountered:
- functional (follicular and corpus luteum) cysts,
- mature cystic teratomas, and
- endometriomas.
- cystadenomas
Ovarian cysts are quite common and affect all age groups, both symptomatic and asymptomatic women. In a study by Campbell et al., six percent of 5000 healthy women reported detectable adnexal masses on a transabdominal ultrasound examination. Of these, 90% were cystic, with most diagnosed as simple cysts. About 8% of premenopausal women develop large cysts that require treatment. According to estimates by the National Institutes of Health, 5-10% of women need surgery to remove an ovarian cyst. Of these cysts, about 13-21% are malignant. A two-year interim analysis of the International Ovarian Tumor Analysis Phase 5 (IOTA5) study showed that 80% of ovarian cysts classified as benign on ultrasound either disappeared or required no intervention. Only 12 of the 1919 women in the study received a diagnosis of ovarian cancer, resulting in a two-year cumulative cancer risk of 0.4%. Ovarian cysts are less common after menopause. Postmenopausal women with ovarian cysts have a higher risk of ovarian cancer. A systematic review and meta-analysis by Liu et al. found that the malignancy rate (including borderline tumors) for simple ovarian cysts in postmenopausal women is about 1 in 10,000.
Functional cysts form in women of reproductive age during folliculogenesis and are of either follicular or corpus luteal origin. These cysts arise during the normal female reproductive process, hence their functional designation. The pathogenesis of follicular cyst formation is complex and related to the release of hormones from the anterior pituitary. In these cases, the traditional feedback mechanisms are not synchronized, and the surge of luteinizing hormone is blunted. As a result, the egg is not released from the follicle, which then does not regress and continues to grow, sometimes to cystic proportions. Corpus luteum cysts develop after ovulation through an unknown mechanism. They can become quite large and twist, which is more often associated with pain and, in some cases, delayed menstruation. Some cysts function autonomously, like those associated with McCune-Albright syndrome, and can reach large sizes.
Mature cystic teratomas or dermoid cysts are actually benign germ cell tumors that are partially cystic. They can occur over a wide age range, with more than 70% occurring during the reproductive years. They are thought to develop from a single primordial germ cell that has completed meiosis I and is arrested in meiosis II. This theory is supported by the anatomical distribution of teratomas along the migration path of primordial germ cells from the yolk sac to the gonadal ridges. MCTs consist of all three germ layers: ectoderm, mesoderm, and endoderm. They are usually unilateral, measuring 2-4 cm in diameter, and are filled with thick sebaceous material, hair, calcifications, and sometimes teeth. Some are even hormonally active. Unlike simple cysts, teratomas do not resolve spontaneously. Most require surgical intervention. They are more commonly associated with ovarian torsion than other benign cysts. Although dermoid cysts are benign, complications upon rupture include chemical peritonitis, bowel adhesions and obstructions, and abscesses.
Endometriomas are hormonally active ovarian cysts whose hormonal changes correspond to the phases of the menstrual cycle. The origin of endometriomas has been controversial. Nezhat and colleagues have proposed that there are two types of endometriomas: primary and secondary. According to the authors, primary endometriomas arise as invaginated surface endometrial glands. They develop slowly over time and rarely reach sizes greater than 5-6 cm. They are difficult to remove during cystectomy due to their fibrous capsule. Microscopic examination identifies both endometrial glands and stroma. Secondary endometriomas arise in functional cysts, with some originating from a corpus luteum. These endometriomas are the classic chocolate cysts and contain dark blood. Secondary endometriomas can become quite large and are easily removed. Microscopic examination of a well-sampled specimen often reveals a corpus luteum, endometrial glands, and stroma.
Cystadenomas are benign epithelial tumors that form cystic structures. They can be serous or mucinous. Serous cystadenomas contain clear, serous fluid and commonly occur in women in their fourth and fifth decades of life. Mucinous cystadenomas are filled with mucinous fluid and can occur unilaterally or bilaterally. These tumors can become large and exert pressure on adjacent organs, leading to symptoms such as bloating, loss of appetite, and constipation. Cystadenomas are typically surgically removed to prevent possible malignant transformation.
Reference:
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