Ovarian Cyst vs. Tumor: Understanding the Crucial Differences

When it comes to ovarian health, distinguishing between an ovarian cyst vs. tumor is crucial. Both can cause similar symptoms, but their implications for your health can be vastly different. 

At Not These Ovaries, we’re committed to demystifying these conditions and empowering you with knowledge. Let’s explore the world of ovarian growths and unravel the complexities together.

The Role of Ovaries in Women’s Health

Before we delve into cysts and tumors, let’s discuss ovaries and ovary function. These essential glands are vital to the female reproductive system, responsible not only for producing eggs but also for creating hormones that regulate various bodily functions. Sometimes, these organs can develop growths that require attention.

Ovarian Cyst vs Tumor: Key Differences

At first glance, an ovarian cyst and an ovarian tumor might seem similar. They’re both growths on or in the ovary and can cause comparable symptoms. However, their nature and potential health implications differ significantly.

An ovarian cyst is a fluid-filled sac that forms on or inside an ovary. Most of the time, these cysts are benign and often resolve on their own. They’re common and frequently occur as part of the normal menstrual cycle. You can learn more about what causes ovarian cysts here.

In contrast, an ovarian tumor is a mass that can be solid, cystic (fluid-filled), or a mix of both.

Take cystadenocarcinoma, for example. It’s a type of tumor that forms in the ovary’s glandular tissue and has multiple fluid-filled spaces. 

So, while people often think tumors are always solid masses, the reality is more complex. Not all tumors are cancerous either; many ovarian tumors are benign. But because tumors can be either benign or malignant (cancerous), and because they can have such varied characteristics, they usually require closer examination by your healthcare team.

The Different Types of Ovarian Cysts

Knowing the different types can help you understand what your doctor is discussing and what to expect.

Functional Cysts

Functional Cysts: These are the most common type and form as part of your normal menstrual cycle. Functional cysts include:

• Follicular cysts: These develop when a follicle (the sac that normally releases an egg) doesn’t rupture during ovulation and continues to grow. Most disappear within one to three months without treatment.
• Corpus luteum cysts: After releasing an egg, the empty follicle usually shrinks. Sometimes it seals off and fluid accumulates inside, creating a corpus luteum cyst. These typically resolve on their own within a few weeks.

The good news? Functional cysts are rarely cancerous and usually cause no symptoms.

Non-Functional Cysts

Non-Functional Cysts: These cysts don’t form as part of the menstrual cycle and may require closer monitoring:

• Dermoid cysts (teratomas): These unusual cysts can contain tissues like hair, skin, teeth, or even bone. They develop from cells present from birth and are most commonly diagnosed in women between ages 20 and 40. While they sound alarming, dermoid cysts are almost never cancerous. However, they don’t disappear on their own and typically require surgical removal.
• Cystadenomas: These develop from cells on the ovary’s surface. Serous cystadenomas contain thin, watery fluid, while mucinous cystadenomas are filled with thick, mucous-like material. These cysts can grow quite large — sometimes up to 12 inches or more — and often attach to the ovary by a stalk rather than growing within it.
• Endometriomas: Often called “chocolate cysts” because they contain dark, thick blood, these form in people with endometriosis. Endometriomas themselves are not cancer. But the relationship between endometriosis and ovarian cancer is real, and research published in 2024 sharpened our understanding of exactly who carries the added risk. More on that below.

How Fast Do Ovarian Cysts Grow Compared to Tumors?

The growth rates of ovarian cysts and tumors can vary significantly.

Ovarian cysts typically grow slowly or not at all. Most functional cysts (those that form during the menstrual cycle) appear and disappear within a few months. Some types of cysts, like endometriomas or dermoid cysts, might persist longer or grow more gradually.

Tumors, however, can be less predictable. Benign tumors often grow slowly, sometimes taking months or years to reach a noticeable size. Malignant tumors, on the other hand, can grow and spread more rapidly. This is why any solid mass requires prompt attention: early detection is crucial for optimal outcomes.

Which Ovarian Cysts May Raise Your Cancer Risk?

It’s important to understand that most ovarian cysts do not increase cancer risk. However, certain findings warrant closer monitoring.

Complex Cysts

Complex cysts have solid areas, dividing walls (septations), or irregular surfaces. Most complex cysts are still benign. But a complex appearance is more likely to reflect cancer than a simple, smooth, fluid-filled sac is, which is why radiologists pay close attention to it. One point of precision matters here: complex cysts don’t turn into cancer. Their appearance is a clue about what may already be there.

Endometriomas

Endometriomas deserve their own paragraph, because the science on them changed recently. A 2024 research study found that women with any form of endometriosis had roughly 4.2 times the risk of ovarian cancer compared with women without it. For women with ovarian endometriomas, deep infiltrating endometriosis, or both, the risk was about 9.7 times higher.

The subtype detail matters even more for our community. That same study found endometriosis was associated with about 7.5 times the risk of type I ovarian cancers, the group that includes low-grade serous ovarian cancer, clear cell, endometrioid, and mucinous tumors. Among women with deep infiltrating endometriosis and/or endometriomas, the risk of type I disease was roughly 19 times higher.

Those multiples sound frightening. Here’s the context that keeps them honest: the baseline lifetime risk of ovarian cancer for women in the U.S. is around 1%. A four-fold increase on a small number is still a small number. 

What this research really tells us is that a specific subset of people, those with endometriomas or deep infiltrating disease, belong in a different conversation with their doctor than someone with mild superficial endometriosis. 

Post-Menopausal Cysts

Post-menopausal cysts were long treated as automatically suspicious. The evidence no longer supports that blanket assumption. What predicts risk is the appearance of the cyst, not the age of the woman it’s found in. We’ll get into the actual numbers in a moment.

Remember, even if you have one of these “higher risk” cysts, it doesn’t necessarily mean you have cancer. What it does mean is that your healthcare provider might want to monitor the situation more closely.

What is the Difference Between an Ovarian Cyst, Ovarian Tumor, and Ovarian Cancer?

Understanding the distinctions between these conditions is crucial for proper health management:

• Ovarian cysts are fluid-filled sacs that can form as part of your normal menstrual cycle or due to other conditions. Most cysts are benign and often resolve on their own without intervention.
• Ovarian tumors are a mass that can be solid, cystic (fluid-filled), or a mix of both. While benign tumors are not cancer, they may still require treatment if they cause symptoms or grow large.
• Ovarian cancer occurs when cells in or near the ovaries grow abnormally and out of control. Ovarian cancer can originate in the ovaries, fallopian tubes, or peritoneum (the tissue lining the abdominal cavity).

It’s worth noting that some ovarian tumors can be borderline, meaning they have characteristics of both benign and malignant tumors. Borderline ovarian cancer, sometimes referred to as ovarian tumors of low malignant potential (LMP), is a unique form of ovarian cancer that falls between benign and malignant tumors and requires careful evaluation and management.

The key takeaway is that not all ovarian growths are the same. While cysts are usually benign, tumors and especially ovarian cancer require prompt and thorough evaluation. This underscores the importance of knowing your body and communicating any changes or symptoms to your healthcare provider.

What Makes Some People More Prone to Ovarian Cysts?

Several factors can increase the likelihood of developing ovarian cysts:

• Age: Ovarian cysts are most common during reproductive years.
• Hormonal imbalances: Conditions like polycystic ovary syndrome (PCOS) can lead to multiple small cysts on the ovaries.
• Endometriosis: This condition, where uterine-like tissue grows outside the uterus, can lead to a type of cyst called an endometrioma.
• Pregnancy: Early pregnancy can sometimes lead to a corpus luteum cyst.
• Pelvic infections: Past infections can increase the risk of developing certain types of cysts.
• Fertility treatments: Some fertility medications can increase the likelihood of developing ovarian cysts.

It’s important to remember that having risk factors doesn’t necessarily mean that you’ll develop cysts. At the same time, not having these risk factors doesn’t ensure you won’t. Each person’s body responds differently to various influences.

How Often Are Ovarian Cysts Cancerous?

The vast majority of ovarian cysts are benign. And what predicts risk isn’t your age or your menopausal status on its own. It’s what the cyst looks like on imaging.

Simple Cysts: Reassuring at Any Age

A landmark study published in JAMA Internal Medicine followed more than 72,000 women who had pelvic ultrasounds. Among the 15,306 women found to have a simple cyst, exactly one was diagnosed with ovarian cancer over the following three years. 

For women 50 and older with a simple cyst, the absolute three-year risk worked out to somewhere between 0 and 0.5 cases per 1,000 women. Statistically, that’s no different from women whose ovaries looked entirely normal.

That includes women past menopause. Simple cysts turned up in roughly 13% of the women aged 50 and older in that study. They’re common, and on their own, they aren’t a warning sign.

This is a real shift from older guidance, which often committed women with simple post-menopausal cysts to years of repeat scans. If you’re still having periods, the reassurance is even stronger: malignancy is found in well under 1% of ovarian cysts in women of reproductive age.

Complex Cysts and Solid Masses: A Different Conversation

Here the risk genuinely does rise. In that same study, women with a complex cyst or a solid ovarian mass faced a meaningfully higher risk: roughly 9 to 11 cases per 1,000 women under 50 over three years. 

Among post-menopausal women with complex cystic or solid masses, researchers estimated that about 6.5% would be diagnosed with ovarian cancer within three years.

Read that number carefully, because it cuts both ways. A complex mass after menopause is a legitimate reason for prompt evaluation. It’s also true that roughly 93 out of every 100 women in that group did not have cancer.

It’s worth noting that even benign cysts can sometimes cause problems. Large cysts can twist or rupture, causing pain and potentially requiring surgical intervention.

Ovarian Tumor vs Cyst Ultrasound: Imaging Insights

An ultrasound is a primary tool for distinguishing between ovarian cysts vs tumors. This imaging technique provides valuable insights into the nature of ovarian growths.

On an ultrasound, simple cysts typically appear as dark, fluid-filled sacs with thin, smooth walls. Simple cysts are characterized by clear fluid content and well-defined borders.

Tumors, conversely, can appear as solid masses or have mixed solid-cystic features. A key differentiating factor is that tumors have their own blood supply, which can be detected on ultrasound. They may also have irregular borders or internal echoes, indicating a more complex structure.

Complex cysts fall between these two categories. They might have solid areas, thick walls, or debris within the fluid, making them more challenging to classify definitively based on ultrasound alone.

While an ultrasound is excellent at revealing the structure of ovarian growths, it can’t always definitively determine whether a mass is benign or malignant. For this reason, doctors may employ additional diagnostic tools, such as the CA-125 blood test or other imaging studies, to form a comprehensive assessment.

What Does the O-RADS Score on Your Report Mean?

If you’ve read your actual radiology report, you may have spotted a line like “O-RADS 3.” It looks like code. It’s actually one of the most useful things on the page.

O-RADS stands for the Ovarian-Adnexal Reporting and Data System. It’s a scoring system from the American College of Radiology that gives radiologists a shared vocabulary for describing ovarian findings, along with an estimated risk of cancer attached to each score. Here’s the plain-language version:

• O-RADS 0 — The evaluation is incomplete. More imaging is needed before anyone can say much.
• O-RADS 1 — A normal physiologic finding, such as a follicle in a premenopausal ovary. Not a concerning cyst at all.
• O-RADS 2 — Almost certainly benign. Estimated cancer risk under 1%.
• O-RADS 3 — Low risk, generally in the range of 1% to under 10%.
• O-RADS 4 — Intermediate risk.
• O-RADS 5 — High risk. Referral to a gynecologic oncologist is generally recommended.

One update is worth knowing about, particularly if you’ve been told you need surgery. In 2022, the American College of Radiology revised the system, and lower-risk O-RADS 3 findings can now be followed with repeat ultrasound rather than automatically removed. The revision also placed more emphasis on MRI for characterizing solid areas, since MRI can be more specific than ultrasound in those cases.

If your report doesn’t include an O-RADS score, you’re allowed to ask for one. And if surgery has been recommended for a low-risk finding, that’s a fair moment to ask for a second opinion.

When a Cyst Turns Out to Be a Borderline Tumor

There’s a category that sits squarely between “harmless cyst” and “ovarian cancer.” It’s also the category Not These Ovaries was built to fund research for: borderline ovarian tumors, sometimes called tumors of low malignant potential.

Borderline tumors have abnormal cells, but those cells don’t invade surrounding tissue the way an invasive cancer does. They also tend to appear decades earlier than high-grade ovarian cancer, frequently in women in their 20s, 30s, and 40s.

On imaging, they can be deceptive. Borderline tumors often show up as a unilocular solid cyst: a single fluid-filled chamber with solid growths, called papillary projections, extending into it. The classic clinical picture is a younger woman with a complex-looking cyst and a CA-125 that’s normal or only mildly elevated. Nothing about that combination announces itself as urgent, which is precisely the problem.

Radiologists have identified one helpful clue. A “microcystic pattern,” meaning tiny fluid-filled spaces within the papillary projections or solid areas, showed up in nearly 90% of surgically confirmed borderline tumors in one study, and in almost all of the serous borderline tumors specifically.

If you’re navigating this now, our guides to borderline ovarian tumor symptoms and borderline ovarian tumors and fertility go deeper.

Fibroid Tumor vs Ovarian Cyst: Distinguishing Features

Fibroids and ovarian cysts can sometimes be mistaken for each other, but they have distinct characteristics:

Fibroids are non-cancerous growths that develop in or on the uterus. They consist of muscle and fibrous tissue and form nodules in the uterine wall. Ovarian cysts, as we’ve discussed, form on or in the ovaries and are typically fluid-filled.

On imaging tests, fibroids and ovarian cysts can appear similar, especially if the fibroid is pedunculated (on a stalk) or if the cyst is particularly large. However, key differences include:

• Location: Fibroids are in the uterus, while cysts are on the ovaries.
• Composition: Fibroids are solid, while cysts are usually fluid-filled.
• Symptoms: Fibroids often cause heavy menstrual bleeding, while cysts are more likely to cause pelvic pain or pressure.

Accurate diagnosis is crucial because the treatment approaches for fibroids and ovarian cysts can differ significantly.

When to Seek Medical Attention

Understanding when to be concerned about ovarian growths is crucial. Here’s a general guide:

Routine Monitoring:

• A simple cyst is found during a routine exam
• The cyst is small (usually less than 5 cm)
• You’re pre-menopausal and have no symptoms
• Your doctor recommends “watchful waiting”

Consult Your Doctor:

• You have persistent pelvic pain or pressure
• You experience changes in your menstrual cycle
• You have bloating or a feeling of fullness that doesn’t go away
• You’re postmenopausal, and a cyst is discovered

Seek Immediate Care:

• You have severe pain with fever and vomiting
• You experience dizziness, weakness, or rapid breathing
• You have sudden, severe abdominal pain

Remember, your body is unique, and what’s normal for one person might not be customary for another. Trust your instincts, and don’t hesitate to consult your healthcare provider if you have concerns.

What is Ovarian Torsion?

One of the most serious complications of ovarian cysts is ovarian torsion, when an ovary twists around the ligaments that support it and cuts off its own blood supply. It’s one of the most common gynecologic surgical emergencies, and it needs treatment fast. The main risk factor is an ovarian mass measuring 5 cm or larger, though torsion can occur with any size cyst, and occasionally with no cyst at all.

If you experience sudden, severe pelvic pain (often on one side) accompanied by nausea and vomiting that doesn’t improve, call 911 or get to an emergency room immediately.

Two things are worth knowing before you get there.

First, a normal Doppler ultrasound does not rule out torsion. The ovary has a dual blood supply, so flow can still appear on a scan during a partial twist. If your pain is severe and your imaging looks normal, that alone isn’t a reason to be sent home without a clear alternative explanation. Say so, plainly.

Second, the outlook is better than it used to be. Current practice is to untwist the ovary and preserve it, even when it looks dark or damaged during surgery. The great majority of ovaries treated this way go on to function normally afterward. Older practice was to remove a torsed ovary on sight, so if you’re facing this conversation, it’s worth asking directly whether preservation is being attempted.

If you suspect something serious, don’t wait for a regular appointment. Seek evaluation from a gynecologic oncologist who specializes in reproductive cancers and can provide expert diagnosis.

Ovarian Cyst vs Tumor: Frequently Asked Questions

Can an ovarian cyst turn into a tumor or cancer? Not in the way most people imagine. A simple, fluid-filled cyst doesn’t transform into cancer over time. When a growth looks complex on imaging, that appearance is a clue about what the mass already is, not a prediction of what it might become. This is why the description in your radiology report matters more than the word “cyst” on its own.

Is a 5 cm ovarian cyst dangerous? Size alone doesn’t determine risk, but 5 cm is a meaningful threshold for one specific reason: ovarian masses 5 cm or larger carry a higher risk of ovarian torsion. A 5 cm simple cyst in a premenopausal woman is usually monitored rather than removed. A 5 cm complex cyst is a different conversation.

Can an ultrasound tell if an ovarian mass is cancer? Ultrasound is very good at describing a mass, and less good at delivering a verdict. It can identify features strongly associated with cancer, such as solid components, irregular borders, and blood flow within the mass. But only pathology, meaning tissue examined under a microscope, provides a definitive answer.

What is a complex ovarian cyst? A complex cyst is one that isn’t purely fluid. It may contain solid areas, internal dividing walls called septations, thick walls, irregular surfaces, or debris. Most complex cysts are still benign, but they warrant closer evaluation than simple cysts do.

Do all ovarian tumors need surgery? No. Many benign ovarian tumors and cysts are monitored with repeat imaging instead. Under the updated O-RADS guidance, even some low-risk findings that were once removed can now be followed with ultrasound. Surgery is more likely to be recommended for masses that are large, persistent, symptomatic, or suspicious on imaging.

Can you have ovarian cancer with a normal CA-125? Yes. CA-125 misses a meaningful number of cancers, and it’s especially unreliable in younger women. Borderline ovarian tumors and low-grade serous ovarian cancer can both present with a normal or only mildly elevated CA-125. It’s also raised by plenty of non-cancerous conditions, including endometriosis, fibroids, pelvic infection, and even menstruation.

Should I see a gynecologic oncologist for an ovarian cyst? Most people with ovarian cysts never need one. Referral is generally recommended when imaging shows features suspicious for cancer, when there’s fluid in the abdomen (ascites), when a pelvic mass feels fixed or nodular on exam, or when CA-125 is elevated in the appropriate clinical context. If surgery is being planned for a mass that might be cancer, having a gynecologic oncologist perform it is associated with better outcomes.

Ovarian Cysts vs. Tumor: Empowering Women Through Knowledge

Understanding the differences between ovarian cysts and tumors is crucial for managing your health effectively. You’re taking an active role in your well-being by recognizing what to look out for and when to seek help.

At Not These Ovaries, we’re dedicated to providing you with accurate information and supporting research that can make a real difference in people’s lives. Whether you’re dealing with a cyst or a tumor or simply have concerns about your ovarian health, remember that you’re not alone on this journey.

We encourage you to keep asking questions, advocate for your health, and spread awareness. Together, we can improve outcomes for ovarian health issues and create a future where these challenges are met with knowledge and effective care.