The normal ovary by nature is a partially cystic structure. Most ovarian cysts develop as consequence of disordered ovulation in which the follicle fails to release the oocyte. The follicular cells continue to secrete fluid and expand the follicle, which over time can become cystic. Ovarian cysts are quite common and involve all age groups, occurring in both symptomatic and nonsymptomatic females. Six percent of 5000 healthy women in a study reported by Campbell et al had detectable adnexal masses on transabdominal ultrasound. Of these, 90% were cystic with most diagnosed as simple cysts.

The ovaries are the female pelvic reproductive organs that house the ova and are also responsible for the production of sex hormones. They are paired organs located on either side of the uterus within the broad ligament below the uterine (fallopian) tubes. The ovary is within the ovarian fossa, a space that is bound by the external iliac vessels, obliterated umbilical artery, and the ureter. The ovaries are responsible for housing and releasing ova, or eggs, necessary for reproduction. For more information about the relevant anatomy, see Ovary Anatomy.

Indeed, ovarian cysts were the fourth most common gynecologic cause of hospital admissions according to a late 1980s study by Grimes and Hughes. Most cysts spontaneously resolve while some will persist. The persistent ovarian cysts are most likely to be surgically managed. The standard surgical approach to presumptively benign ovarian cysts is the laparoscopic ovarian cystectomy. Indeed, it is one of the most common procedures performed by the practicing obstetrician gynecologist.

In this article, the pathophysiology of ovarian cysts is briefly reviewed to provide a foundation for understanding the ovary and benign cyst formation. The remainder of the article concentrates on the patient evaluation and surgical approaches to cyst removal.

Pathophysiology of ovarian cyst formation
Obstetrician-gynecologists and surgeons most commonly encounter 3 types of benign ovarian cysts. They include functional (follicular and corpus luteum) cysts, mature cystic teratomas, and endometriomas. Functional cysts form in reproductive-aged females during folliculogenesis and are either follicular or corpus luteal in origin.

The cysts occur during the process of normal female reproductive physiology, hence their functional designation. The pathogenesis of follicular cyst formation is complex and is associated with the release of anterior pituitary hormones. In these cases, the traditional feedback mechanisms are not synchronized and the luteinizing hormone surge is muted.

Consequently, the oocyte is not released by the follicle, which in turn fails to involute and continues to grow, sometimes achieving cystic proportions. Corpus luteum cysts develop after ovulation through an unknown mechanism. They can become quite large and torsed and, thus, are more likely to be associated with pain and in some cases delayed menses. Some cysts autonomously function such as those associated with the McCune-Albright syndrome and can achieve large sizes.

Mature cystic teratomas (MCTs) or dermoids are actually benign germ cell tumors that are partially cystic. They can occur over a broad range of ages, yet more than 70% occur during the reproductive years. They are thought to develop from a single primordial germ cell that has completed meiosis I and is meiosis II-suppressed. This theory is supported by the anatomic distribution of teratomas throughout the migration pathway of primordial germ cells from the yolk sac to the gonadal ridges MCTs are composed of all 3 germ layers: ectoderm, mesoderm, and endoderm. They are usually unilateral, measure 2-4 cm in diameter, and are filled with thick sebaceous material, hair, calcifications and sometimes teeth (see images below). Some are even hormonally active. Unlike simple cysts, MCTs do not resolve spontaneously. Most require surgical intervention. They are more likely than other benign cysts to be associated with ovarian torsion.


Laparoscopic Right ovarian cystectomy of a 15 cm benign cystadenoma for a 13 year old girl



References:
http://emedicine.medscape.com/article/1848505-overview