Most ovarian tumors are not cancerous. Roughly 70% to 80% of ovarian masses turn out to be benign, meaning they are noncancerous growths that don’t spread to other tissues. Of the remainder, some are borderline (slow-growing with low risk of spreading), and a smaller fraction are truly malignant. The exact risk depends heavily on your age, family history, and what the mass looks like on imaging.
How Ovarian Tumors Break Down
When doctors find a mass on or near an ovary, it falls into one of three broad categories: benign, borderline, or malignant. Benign tumors, including functional cysts, dermoid cysts, and certain fluid-filled growths, make up the majority. Many resolve on their own or require only minor treatment.
Borderline ovarian tumors sit between benign and cancerous. They have some abnormal cell features but typically don’t invade surrounding tissue the way true cancers do. These account for about 15% of all epithelial ovarian tumors, the most common cell type. Borderline tumors tend to be diagnosed at a younger age and carry a significantly better prognosis than invasive cancer.
Fully malignant ovarian cancers represent the smallest share of all ovarian masses, but they are the most serious. Among confirmed ovarian cancers, about 90% are epithelial (arising from the surface layer of the ovary), 5% to 6% are sex cord-stromal tumors, and 2% to 3% are germ cell tumors. In parts of Africa and Asia, germ cell tumors account for a larger proportion, between 10% and 15% of cases.
Age Changes Your Risk Significantly
In premenopausal women, the vast majority of ovarian masses are benign. Functional cysts related to the menstrual cycle are extremely common and almost always harmless. Younger women are more likely to develop dermoid cysts or other benign growths that may need monitoring but rarely turn out to be cancer.
After menopause, the calculus shifts. The ovaries are no longer producing eggs, so any new mass is more suspicious. A postmenopausal woman with an ovarian mass faces a meaningfully higher chance that it’s malignant compared to a woman in her 20s or 30s with a similar finding on ultrasound. Ovarian cancer risk in the general population is about 1.1% over a lifetime, and most cases are diagnosed after age 50.
Genetic Factors That Raise the Odds
Certain inherited gene changes dramatically increase lifetime ovarian cancer risk. Women who carry a harmful BRCA1 mutation have a 39% to 58% chance of developing ovarian cancer over their lifetime. For BRCA2 carriers, the range is 13% to 29%. Compare that to the 1.1% baseline risk for the general population, and the difference is striking.
These numbers don’t mean that every ovarian mass found in a BRCA carrier is cancerous. But they do mean that doctors take ovarian findings in these patients more seriously and may recommend earlier intervention, including preventive removal of the ovaries and fallopian tubes once childbearing is complete.
How Doctors Assess Whether a Tumor Is Cancerous
Ultrasound is the first tool used to evaluate an ovarian mass. A standardized set of imaging criteria known as the IOTA Simple Rules helps doctors classify masses as likely benign or likely malignant based on features like internal blood flow, solid components, and irregular borders. A large meta-analysis covering nearly 8,000 masses found these rules achieve about 92% sensitivity and 92% specificity, meaning they correctly identify most cancers and most benign tumors. The rules work well for about 86% of masses; the rest need further evaluation.
Blood tests measuring a protein called CA-125 are sometimes used alongside imaging. However, CA-125 is not reliable enough for screening on its own. Many noncancerous conditions raise CA-125 levels, including endometriosis, uterine fibroids, liver disease, pelvic inflammatory disease, menstruation, and pregnancy. An elevated result in a premenopausal woman is particularly unreliable, since so many common conditions can cause a false alarm. For this reason, CA-125 is most useful when combined with imaging findings and clinical context, not as a standalone test.
The only definitive way to confirm whether a tumor is cancerous is to examine the tissue, either through a biopsy or after surgical removal.
Survival Rates When Cancer Is Confirmed
If an ovarian tumor does turn out to be malignant, the outlook depends on the cancer type and how far it has spread at diagnosis.
For invasive epithelial ovarian cancer, the most common type, five-year survival rates based on data from 2015 to 2021 are:
- Localized (confined to the ovaries): 92%
- Regional (spread to nearby structures): 71%
- Distant (spread to the liver, lungs, or other distant sites): 32%
- All stages combined: 51%
Rarer tumor types carry considerably better outcomes. Germ cell tumors of the ovary have a 93% overall five-year survival rate, reaching 98% when caught before spreading. Stromal tumors have a 91% overall five-year survival rate. These types tend to occur in younger women and respond well to treatment.
The overall survival figure for epithelial ovarian cancer is weighed down by the fact that many cases aren’t caught until the cancer has already spread. Ovarian cancer is notoriously difficult to detect early because symptoms like bloating, pelvic discomfort, and changes in appetite or urination overlap with dozens of everyday conditions. When found at the localized stage, though, survival rates are high across all tumor types.
What These Numbers Mean for You
If you’ve been told you have an ovarian mass, the statistics are in your favor. The majority of ovarian tumors are benign, particularly if you are premenopausal and the mass has simple, fluid-filled features on ultrasound. Even among masses that look more complex, many turn out to be borderline rather than invasive cancer.
Your individual risk profile matters more than population-level percentages. A 25-year-old with a smooth, cyst-like mass on ultrasound and no family history faces a very different situation than a 60-year-old with an irregular solid mass and elevated blood markers. The combination of age, imaging characteristics, family history, and lab results is what guides your doctor’s next steps, whether that’s watchful waiting with a repeat ultrasound in a few weeks or surgical evaluation.