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Ovarian Cyst vs. Ovarian Cancer: What’s the Difference?  | Dana-Farber Cancer Institute

Published: December 1, 2023

Written by: Beth Dougherty

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An ovarian cyst is not the same as ovarian cancer. Benign ovarian cysts are extremely common, while ovarian cancer is rare. They do share symptoms, such as abdominal bloating, pressure, pain, or swelling.  

A gynecologist can help you determine if you have a benign ovarian cyst and if you need treatment. Many cysts go away on their own. Very few, less than 1%, are cancerous. A gynecologist will refer you to a gynecologic oncologist for more diagnostics if cancer is a possibility.  

What is an ovarian cyst? 

An ovarian cyst is a fluid-filled sac that appears on an ovary. A “cyst” refers to the structure of mass but may be benign (non-cancerous) or malignant (cancerous).  

Benign ovarian cysts normally form during monthly ovulatory cycles. These cysts are called “functional cysts.” They are not cancerous, don’t cause noticeable symptoms, and usually go away on their own.  

Functional cysts form when an ovary grows a cyst, called a follicular cyst, that contains hormones that are needed to release an egg from the ovary. When the sac bursts, the egg leaves the ovary and travels down the fallopian tube.  

After ovulation, the sac transforms into a different type of cyst which produces the hormone progesterone to support a possible pregnancy. These cysts, called corpus luteum cysts, usually go away on their own after the next period.  

Although functional cysts are not cancerous, if they grow large, they can cause pain, bleeding, or pelvic pressure. Rarely, an ovarian cyst can cause the ovary to twist, a rare condition called ovarian torsion. Ovarian torsion is severely painful, can cause nausea and vomiting, and is a medical emergency.  

What is ovarian cancer? 

Ovarian cancer occurs when cancerous cells form a mass in the tissue of the ovary or the fallopian tube. Ovarian cancer is a complex disease with several subtypes and treatments. Treatment may involve surgery, chemotherapy, or both.  

Getting a detailed diagnosis is essential to get the right treatment. Learn more about ovarian cancer diagnosis and treatment at Dana-Farber Brigham Cancer Center here.  

What are the symptoms of an ovarian cyst or ovarian cancer? 

The signs and symptoms for benign ovarian cysts and ovarian cancer are very similar. They can include: 

  • Pain or swelling in the abdomen 
  • Gastrointestinal problems, such as feeling full quickly during meals, gas, bloating, diarrhea, and/or constipation 
  • Abdominal or pelvic pain, or pain during intercourse 
  • Shortness of breath 

Sharp abdominal pain accompanied by fever and nausea can be a sign that an ovarian cyst has ruptured or twisted. If you experience these symptoms, please visit the local emergency room. 

How are ovarian cysts and ovarian cancer diagnosed? 

A doctor will normally order a transvaginal ultrasound to look at the ovaries. Using this imaging technique, the doctor can determine if there is a mass on the ovary and can assess its size, shape, location, and other features. 

A cyst will appear to be filled with fluid. Benign ovarian cysts usually are relatively simple in structure and have very little blood flow to the internal components.   

In contrast, cancerous masses often have both cystic and solid components. The shapes tend to be more complex, and there may be signs of increased flow to the internal parts.  

A doctor might also order a CA125 blood test. The CA125 protein tends to be elevated in many types of ovarian cancer, though it can also be elevated in benign conditions such as endometriosis, fibroids, or pelvic inflammatory disease.  

What causes an ovarian cyst? 

Certain factors can increase the possibility of an ovarian cyst: 

  • Hormonal drugs designed to promote ovulation. 
  • Endometriosis, in which the lining of the uterus grows outside of the uterus and can result in an ovarian cyst called an endometrioma 
  • Pelvic infections. 
  • Pregnancy. Ovarian cysts may form temporarily early in pregnancy. 
  • Polycystic ovarian syndrome (PCOS) results in the formation of many small cysts on the ovaries. 
  • Anovulation. Any medical condition which disrupts normal ovulatory and menstrual patterns may cause functional cysts to form but not resolve on their own.  
  • Age. Ovarian cysts are more common before menopause. An ovarian cyst after menopause is more likely to be cancerous than one that occurs before menopause. 

How are ovarian cysts treated? 

If the cyst is not painful, a doctor might suggest watching the cyst to see if it disappears after a few months. Another alternative is surgical removal.  

Your doctor may refer you to a gynecologic oncologist if there is a concern that a mass could be cancerous. Learn more about Dana-Farber Brigham’s Gynecologic Oncology Program

What causes ovarian cancer? 

The causes are unknown, but several factors contribute to an increased risk: 

  • Family history or an inherited mutation such as BRCA1 or BRCA2 that increases risk  
  • Age, as older women have a higher risk 
  • Early start of menstruation or delayed menopause 
  • Polycystic ovarian syndrome 
  • Endometriosis 

There are also several factors that decrease ovarian cancer risk: 

  • Pregnancy 
  • Breastfeeding 
  • Use of oral contraceptive pills 
  • Tubal ligation 

Learn more about ovarian cancer diagnostics and ovarian cancer treatment at Dana-Farber Brigham. 

Learn more about Breast and Ovarian Cancer Genetics and Prevention at Dana-Farber Brigham. 

Learn more about the Centers for Early Detection and Interception at Dana-Farber.  

Take Dana-Farber’s AssessYourRisk Quiz to learn more about your personal risk of ovarian cancer. 

About the Medical Reviewer

Kevin M. Elias, MD

Dr. Elias is a gynecologic oncologist and surgeon-scientist at Dana-Farber and Brigham and Women’s Hospital. He treats women with all types of gynecologic cancer. His areas of expertise are gestational trophoblastic disease, familial cancer syndromes, and ovarian cancer.