Ovarian Cysts

Ovarian Cysts

Clinically reviewed Aug 29, 2026 Updated Aug 30, 2026
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Clinical Snapshot

An ovarian cyst is a fluid-filled sac on or within the ovary. In everyday pharmacy and primary care practice, the overwhelming majority are functional cysts — a normal, physiologic byproduct of the ovulatory cycle rather than a disease process: a follicular cyst forms when the dominant follicle of the cycle fails to rupture and release an egg and instead continues to fill with fluid, while a corpus luteum cyst forms when the corpus luteum that remains after ovulation fails to regress on schedule, or bleeds internally into itself. Functional cysts are common enough that they are frequently found incidentally on pelvic ultrasound performed for an unrelated reason, and the great majority resolve spontaneously within one to three menstrual cycles without any treatment at all.[1]

This chapter is deliberately organized around a single central tension. On one side, the two current SOGC guidelines on this topic — Guideline No. 403 on the initial investigation of adnexal masses, and Guideline No. 404 on the management of benign ovarian masses specifically — are explicit that the correct default for most patients is conservative, expectant management, and that reducing unnecessary surgery is a genuine goal of good guideline-based care here, not simply a cost consideration.[2][1] On the other side, a genuine minority of presentations are the opposite of routine: ovarian torsion and a ruptured hemorrhagic cyst are surgical emergencies that must be recognized promptly (see Red Flags & Refer), and a small number of adnexal masses — more often, though not exclusively, in postmenopausal patients — carry genuine features of malignancy that change the entire management pathway (see Assessment & Diagnosis). Getting both halves right — treating the common, benign, self-limited presentation as exactly that, while never missing the uncommon emergency or the uncommon cancer risk — is the actual skill this chapter is trying to build.

This chapter focuses on functional cysts and provides a differential overview of the other benign adnexal masses most likely to be confused with them on ultrasound — endometrioma, mature cystic teratoma (dermoid cyst), and cystadenoma — along with the features that should raise concern for malignancy. It does not duplicate this platform's separate Ectopic Pregnancy chapter; where the two conditions overlap in presentation, this chapter cross-references that content rather than repeating it.

Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.

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