Ovarian cysts are defined as “a sac or pouch filled with fluid or other tissue that forms in or on an ovary.”1 The demographic most affected by ovarian cysts is premenopausal women of child-bearing age, although fetal, prepubescent, and postmenopausal women may also be diagnosed.2-4 Overall, the risk of developing a benign, adnexal mass is common in women of all ages, affecting up to 90% of premenopausal women and 75% of postmenopausal women.5

There are 4 types of ovarian cysts:  functional, endometrioma, teratoma, and cystadenoma.1

  • Functional ovarian cysts comprise the majority of cases and develop either during ovulation when a follicle continues to grow rather than rupturing and releasing an ovum or when the corpus luteum continues to grow instead of undergoing involution.1,5
  • Endometriomas develop from a hemorrhage of endometriosis tissue, resulting in a chocolate-colored fluid filling the cystic sac, which may be encased by epithelial tissues that become fibrous.6
  • Teratomas may be composed of hair follicles, lung tissue, muscle tissue, or skin that cause the cyst to appear very dense on ultrasound.5,7 Teratomas, though usually benign, can be cancerous in which case they are composed of immature rather than mature tissues. A dermoid cyst, the most common type of teratoma, is also the most common germ-cell tumor in women.5
  • Cystadenomas are serous tumors made of multiple cysts and are generally benign, although they may become greatly enlarged compared to the other types of ovarian cysts.8

Clinical Features and Diagnosis

In most cases, ovarian cysts are found incidentally on ultrasound, though there are patients that present with pain in their lower abdomen and/or pelvis.1,5 Figures 1-4 provide examples of ultrasound images of ovarian cysts.9-12


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Figure 1. A 2-cm left ovarian cyst.9

Figure 2. Figure 2. Teratoma dermoid cyst.10

Figure 3. Endometrioma.11

Figure 4. A 5-cm left ovarian cyst.12