Colon Cancer in Ovaries Versus Ovarian Cancer

Misdiagnosed Metastatic Colon Cancer

Woman speaking with doctor
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Colon cancer that has spread (metastasized) to your ovaries and primary ovarian cancer are completely different things, though it may be difficult to tell the difference. Here's what you need to know to empower yourself as a patient.

Colon Cancer Metastatic to the Ovaries

Studies have shown that not only is colon cancer the most common type of cancer to metastasize to the ovaries, but between 4 percent and 30.8 percent of patients with primary colon cancer end up with ovarian metastases.

Most colon cancers that metastasize to the ovary have extended through the full thickness of the bowel wall and have spread to mesenteric lymph nodes.

Colon Cancer Metastatic to the Ovaries Is Often Misdiagnosed as Primary Ovarian Carcinoma

If you have a history of colon cancer and you develop ovarian masses, you need to be wary of a diagnosis of a new primary cancer in the ovary, especially if the tumor involves both ovaries and is reported to be endometrioid or mucinous carcinoma. Some of these ovarian metastases can be predominantly cystic and may have benign-appearing areas when they're examined under the microscope, which can easily mislead your doctor and pathologist. This is a very tricky area of pathology, and unless the pathologist has made a specific effort to become familiar with this problem, it's likely that colon cancer metastatic to the ovaries will be misinterpreted as a primary ovarian tumor.

How Misdiagnosis Happens

Under the microscope, it can sometimes be difficult to tell what type of cells you're looking at. Cancer cells are by definition abnormal appearing. In fact, sometimes it's hard to tell where a cancer cell originated because it looks so abnormal. Doctors use the term differentiation to describe this.

A well-differentiated tumor, for example, may look a lot like the tissue in which cancer began, while a highly undifferentiated cancer may not resemble any normal cells in our bodies. On top of being undifferentiated, some tissues in our bodies resemble other tissues, so cancer cells from two different organs may resemble each other.

The Risk of Misdiagnosis

You are more at risk of misdiagnosis if your pathologist is unfamiliar with your history. To facilitate the correct diagnosis, it's essential that your pathologist is informed of your history of colon cancer, which in most cases will be known or found at the same time as the ovarian tumor(s). However, there are occasional cases that are particularly treacherous in which surgical treatment for presumed ovarian cancer precedes identification of the colon cancer. Even in these cases, there are particular clues that the experienced pathologist can identify under the microscope that suggest metastatic colon cancer, and special stains can be used to further substantiate the diagnosis.

When Colon Cancer Is More Likely Than Ovarian Cancer

If you're diagnosed with primary ovarian carcinoma of the endometrioid or mucinous type involving both ovaries, or extending to involve any other tissue beyond the ovary, you should request an expert second opinion on your pathology slides to exclude the possibility of metastatic cancer originating from the colon or elsewhere.

If you have a known history of colon cancer, then an expert second opinion is warranted even if only one ovary is involved by endometrioid or mucinous carcinoma. An additional red flag is the finding of metastases within the substance of the liver, which is typical of metastatic colon cancer and almost unheard of for metastatic ovarian cancer.

Be Active In Your Care

No one wants to be told that their colon cancer has spread to their ovaries, but it's better to be diagnosed correctly than to undergo a separate treatment protocol for incorrectly diagnosed primary ovarian cancer. Ask questions. Learn about your cancer.

Consider getting second opinions, not only with regard to surgery and medical oncology, but with your pathology report and diagnosis as well. Take an active part in your care and empower yourself by being your own advocate in your healthcare.


Lee K-C, Lin H, ChangChien C-C, et al. Difficulty in Diagnosis and Different Prognoses Between Colorectal Cancer With Ovarian Metastasis and Advanced Ovarian Cancer: an Empirical Study of Different Surgical Adoptions. Taiwanese Journal of Obstetrics and Gynecology. February 2017;56(1):62-67. doi:10.1016/j.tjog.2015.02.009.

Macrae FA, Bendell J. Clinical Presentation, Diagnosis, and Staging of Colorectal Cancer. UpToDate. Updated August 15, 2017.