Ovarian cyst

3 things to know first

1. Most ovarian cysts are not cancer. The majority are functional cysts linked to the normal menstrual cycle.
2. Size and features matter most. Simple, small cysts often go away on their own, while complex or persistent cysts may need closer follow-up.
3. They are very common. Many women have ovarian cysts at some point, often without knowing.

What it is

An ovarian cyst is a fluid-filled sac that develops on or within an ovary. The most common type is a functional cyst, which forms during the normal menstrual cycle. These include follicular cysts, which develop when a follicle does not release an egg, and corpus luteum cysts, which form after ovulation. Other types include endometriomas, dermoid cysts, and cystadenomas.

Why it appears on your report

Ovarian cysts are commonly seen on pelvic ultrasound and MRI. The radiologist describes the cyst's size, whether it is filled with simple fluid or has solid areas or septations, and whether it looks typical or atypical. This information helps your doctor decide whether monitoring or further testing is needed.

How serious is it

The seriousness depends on the type, size, and features of the cyst:

• Simple cysts smaller than about 5 cm in premenopausal women are usually benign and often resolve within a few menstrual cycles.
• Cysts that are larger, have solid parts, thick walls, or internal septations may need closer evaluation.
• Postmenopausal women have a higher chance of cysts being other than functional, so follow-up is often more cautious.

Most ovarian cysts do not turn into cancer, but your doctor will use imaging features and your history to assess risk.

When to seek care urgently

Seek urgent care if you have:

• Sudden, severe pelvic or abdominal pain
• Pain with nausea and vomiting
• Fainting, dizziness, or signs of internal bleeding
• Fever with pelvic pain
• Shoulder pain with severe abdominal pain

These can be signs of cyst rupture, bleeding, or ovarian torsion, which need prompt evaluation.

What usually happens next

1. Repeat ultrasound. For a simple cyst in a premenopausal woman, a follow-up scan in 6–12 weeks is common to confirm it has resolved.
2. Blood tests. Tumor markers such as CA-125 are sometimes checked, especially after menopause or if the cyst looks complex.
3. MRI if needed. MRI can provide more detail when ultrasound is unclear.
4. Gynecology referral or surgery. Large, growing, or complex cysts may be evaluated by a specialist, and some are removed surgically.

A simple analogy

Think of a functional ovarian cyst like a small water balloon that forms and usually deflates on its own each month. Most of the time it causes no trouble and disappears without anyone noticing.

Further reading

• NHS — Ovarian cyst
• Mayo Clinic — Ovarian cysts