Understanding your colorectal cancer pathology report

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was reviewed on June 9, 2022.

What is a pathology report?

A pathologist is a medical doctor who analyzes cells, organs and tissues, as well as lab tests. A pathologist writes a pathology report to provide information about a tissue sample (or specimen) taken from the body—in this case, from a tumor.

The results from a pathology report can help determine whether:

  • Cancer is present
  • Cancer may spread to other parts of the body
  • A noncancerous tumor may grow

If you have colorectal cancer, a pathology report may help you better understand the diagnosis.

What are common terms in a colorectal cancer pathology report?

A colorectal cancer pathology report may contain terms that are unfamiliar to you and your caregiver. Below are definitions of terms that may be included in the report.

Parts of the colon

The colon is the biggest part of the large intestine. It begins with the cecum, where the small intestine connects to the large intestine, and ends with the sigmoid colon, where the colon connects to the rectum. Between the cecum and the sigmoid colon are the ascending colon, transverse colon and descending colon.


Differentiation refers to the cancer’s grade—or how abnormal the cancer cells appear under a microscope. Usually, cancer cells are characterized by one of three grades:

  • Well-differentiated (low-grade)
  • Moderately differentiated (intermediate-grade)
  • Poorly differentiated (high-grade)

Poorly differentiated cancers typically spread more quickly. Though each grade has specific characteristics, some reports group low and intermediately differentiated cells together as being well-moderately differentiated (low-grade).


Dysplasia means abnormal cells have been detected in the colon. Dysplasia ranges from low- to high-grade depending on how abnormal the cells look under a microscope. The more abnormal they look—the more they look like cancer—the higher (or more severe) the grade.

With high-grade dysplasia, a follow-up colonoscopy may be needed sooner than would be recommended for low-grade dysplasia.


Glands in the colon produce mucin for lubrication. Cancer that makes a lot of mucin is called mucinous (or colloid) adenocarcinoma (cancer that starts in the glands). The presence of mucin doesn’t usually affect treatment decisions.


A polyp is a growth in the colon’s interior lining. Not all polyps are cancerous.

An adenoma polyp (or adenomatous polyp) may look like the lining of the colon. The differences between the two are more obvious under a microscope.

Sessile and serrated refer to how a polyp grows. Sessile polyps look somewhat flattened and broad. Serrated polyps have jagged edges, like a saw. There are two types of serrated polyps: sessile serrated adenomas and traditional serrated adenomas.


Invasive colon cancer has spread beyond the colon’s inner lining. Considered a true cancer, this disease may spread to other body parts if it’s not detected in its early stages.

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