Understanding Your Pathology Report: Invasive Adenocarcinoma of the Colon

When your colon was biopsied, the samples taken were studied under the microscope by a specialized doctor with many years of training called a pathologist. The pathologist sends your doctor a report that gives a diagnosis for each sample taken. This report helps manage your care. The questions and answers that follow are meant to help you understand the medical language used in the pathology report you received for your biopsy. They do not cover all of the information that would be in a pathology report that would result from having part of your colon removed (resected) to treat colon cancer.

What if my report mentions cecum, ascending colon, transverse colon, descending colon, sigmoid colon, or rectum?

The cecum is the beginning of the colon where the small intestine empties into the large intestine. The ascending colon, transverse colon, descending colon, sigmoid colon, and rectum are other parts of the colon after the cecum. The colon ends at the rectum and waste exits through the anus.

What is adenocarcinoma of the colon?

Adenocarcinoma is a type of cancer that starts in the cells that form glands making mucus to lubricate the inside of the colon and rectum. This is the most common type of colon cancer.

What do the words invasive or infiltrating mean?

As colon cancer grows and spreads beyond the inner lining of the colon (mucosa), it is called invasive adenocarcinoma. Cancers that are invasive are called true cancers because they can spread to other places in the body.

Does this mean that the tumor has invaded deeply and is associated with a poor prognosis?

Not always. All this means is that it is a true cancer. A biopsy only samples part of a tumor and so can’t always show how deeply the tumor has invaded. In order to know how far the cancer has invaded, the pathologist needs to have the entire tumor (removed at surgery).

What does differentiation mean?

Differentiation is the grade of the cancer and it is based on how abnormal the cells look under the microscope. Cancers that are higher grade or poorly differentiated tend to be more aggressive – to grow and spread more quickly. Colon cancer is usually divided into 3 grades:

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

Sometimes, though, it is just split into 2 grades: well-moderately differentiated (low grade) and poorly differentiated (high grade).

What is the significance of the grade of colon cancer?

Grade is one of the many factors used to help predict how aggressive a given cancer is (how likely it is to grow and spread). Poorly differentiated (high-grade) colon cancers tend to be more aggressive than well and moderately differentiated colon cancers. However, other factors are also important, such as how far the cancer has spread (which cannot be determined on the biopsy).

What does it mean if there is vascular, lymphatic, or lymphovascular invasion?

These terms mean that cancer is present in the vessels (arteries, veins, and/or lymphatics) of the colon and that there is an increased chance that cancer could have spread out of the colon. However, this doesn’t mean that your cancer has spread or is not curable. The presence of this type of invasion may be a factor in what type of treatments are recommended after the cancer is removed.

What is a polyp?

A polyp is a projection (growth) of tissue from the inner lining of the colon into the lumen (hollow center) of the colon. Different types of polyps look different under the microscope. Polyps are benign (non-cancerous) growths, but cancer can start in some types of polyps.

What does it mean if, in addition to cancer, my report says there are also other polyps such as adenomatous polyps (adenoma) or hyperplastic polyps?

Polyps are very common and some may need to be removed. If they are present in addition to cancer elsewhere in the colon, they don’t usually affect the treatment or follow-up of the cancer.

What does it mean if mucin or colloid is mentioned in my report?

Mucin is produced by the colon to help lubricate the colon. Colon cancers that produce large amounts of mucin are referred to as mucinous or colloid adenocarcinomas. Typically when it is present on a biopsy, it will not affect treatment.

What does it mean if my biopsy report mentions special studies such as microsatellite instability and MSH2, MSH6, MLH1, and PMS2?

In some colon cancers, special laboratory testing may reveal an abnormality referred to as microsatellite instability or MSI. Microsatellite instability is associated with defects (mutations) in several genes including MSH2, MSH6, MLH1, and PMS2. These gene defects can lead to a disease called hereditary non-polyposis colon cancer (HNPCC) or Lynch syndrome. If your cancer is found to have MSI, your doctor may recommend genetic counseling and testing for this disease.

MSI test results may affect your treatment, for example early-stage cancers with MSI may need to be given more aggressive treatment than other early-stage cancers.

This series of Frequently Asked Questions (FAQs) was developed by the association of Directors of Anatomic and Surgical Pathology to help patients and their families better understand what their pathology report means. These FAQs have been endorsed by the College of American Pathologists (CAP) and reviewed by the American Cancer Society.

Learn more about the FAQ Initiative

Last Medical Review: October 14, 2014 Last Revised: October 14, 2014

Copyright 2011 Association of Directors of Anatomic and Surgical Pathology, adapted with permission by the American Cancer Society.