Colon Cancer in Ovaries vs Ovarian Cancer

Misdiagnosed Metastatic Colon Cancer

Woman speaking with doctor
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When do you have colon cancer that has spread (metastasized) to your ovaries, and when do you have a primary ovarian cancer?  It may seem surprising to be asking that question, but it is a big concern.  Medicine isn't always black and white.

Colon Cancer Metastatic to the Ovaries

The ovaries in patients with colon cancer are occasionally involved by metastatic disease. 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

Women with a history of colon cancer who develop ovarian masses need 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 examined under the microscope, which can easily mislead the patient's doctor and the 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 is likely that colon cancer metastatic to the ovaries will be misinterpreted as a primary ovarian tumor.

How Can This Happen? Isn't the Type of Cancer Obvious?

Under the microscope, it can sometimes be difficult to tell what type of cells you are looking at.

  Cancer cells are by definition abnormal appearing. In fact, sometimes it is hard to tell where a cancer cell it 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 beginning undifferentiated, some tissues in the bodies resemble other tissues, so cancer cells from 2 different organs may resemble each other.

Who Is at Risk of Misdiagnosis?

People are more at risk of misdiagnosis if their pathologist is unfamiliar with their history. To facilitate the correct diagnosis, it is essential that the pathologist is informed of the patient's 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 suggests metastatic colon cancer, and special stains can be used to further substantiate the diagnosis.

When is it More Likely to Be Colon Cancer Than Ovarian Cancer?

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

If the patient has 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.

Bottom Line

No one wants to be told that their colon cancer has spread to their ovaries, but it is 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 of your pathology report and diagnosis as well.  Take an active part in your care, and empower yourself by being your own advocate in your health care.


Macrae, F., and J. Bendell. Clinical presentation, diagnosis, and staging of colorectal cancer. UpToDate. Updated 02/04/16.

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