Understanding colon cancer

A colon cancer is detected in about 2 to 6 out of every 1000 people older than 50 having a colonoscopy. Having a close family member (parent, brother or sister) who developed colon cancer is associated with increased risk. The rate of colon cancer increases as people grow older. Older people with bleeding from rectum and/or iron deficiency anemia are also more likely to have colon cancer.

Over a person’s lifetime the risk of dying from colon cancer is modest. About 30 in 1000 people in the population will die from colon cancer.

Effective treatment approaches for colon cancer are available, especially when detected early, and they are usually started shortly after diagnosis.

If you receive a diagnosis of colon cancer, you may receive a report with some unfamiliar terms. If you want to learn more about this, the following questions and answers explain terms that you may see in a report.

1. What is adenocarcinoma of the colon?
Adenocarcinoma of the colon is the most common type of colon cancer (malignant tumor). Adenocarcinoma has a wide range of behavior from cases that are very slow growing with a low risk of causing harm, to cases that are more aggressive and can spread to other areas of your body.
2. What does “invasive” or “infiltrating” mean?
As colon cancer grows and spreads beyond the inner lining of the colon (mucosa), it is called “invasive adenocarcinoma”. It then has the potential to spread to other places in the body.
3. Does this mean that the tumor has invaded deeply and is associated with a poor prognosis?
Not necessarily. On a biopsy, the pathologist cannot typically determine the depth of tumor invasion. The depth of tumor invasion as well as prognosis are typically determined when the entire tumor is subsequently removed or by CT scan.
4. What does differentiation refer to?
Differentiation is the grade of the cancer and is determined by its microscopic appearance. It is an indication of the aggressiveness of the cancer. Colon cancer is usually divided into three grades (well differentiated, moderately differentiated, and poorly differentiated) or sometimes two grades (well-moderately differentiated and poorly differentiated).
5. What is the significance of the grade of colon cancer?
Grade is one of the many factors that helps determine the aggressiveness of a given cancer. Poorly differentiated colon cancers tend to be more aggressive than well and moderately differentiated colon cancers. However, other factors in addition to grade, such as how far the cancer has spread (which cannot be determined on the biopsy) also affect the prognosis.

If poorly differentiated colon cancer is present in a polyp, an operation performed by a surgeon may be recommended to make sure that the tumor has not spread outside of the colon.
6. 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 spread out of the colon. However, your cancer could still be very curable depending on other factors.

When vascular or lymphovascular invasion is present in a cancer occurring in a polyp, then an operation performed by a surgeon may be recommended to make sure the tumor has not spread outside of the colon.
7. What does it mean if, in addition to cancer, my report says there are also other polyps such as adenomatous polyp (adenoma) or hyperplastic polyps?
Polyps are very common and in the setting of cancer elsewhere in the colon will typically not affect treatment and are nothing to worry about.
8. What is the significance 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. However, on a biopsy specimen, the presence of “mucin” or “colloid” will not determine prognosis or treatment.
9. 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”’. Microsatellite instability is associated with several proteins including MSH2, MSH6, MLH1, and PMS2. Microsatellite instability may be due to a genetic defect that could be present in other family members. At times, additional tests may be necessary and your doctor can help determine when these are needed. Your doctor may use these test results to modify your treatment plan (type, or use, of chemotherapy) or to direct testing of other family members.
10. What is an adenoma?
An adenoma is a type of polyp that resembles the normal lining of your colon but differs in several important microscopic aspects. In some cases, a cancer can arise in the adenoma.
11. What if my report mentions “tubular adenoma”, “tubulovillous adenoma”, “villous adenoma”, “sessile serrated adenoma”, “sessile serrated polyp”, or “traditional serrated adenoma, adenomatous polyp, or hyperplastic polyp” in relation to my cancer?
Adenomas have several different growth patterns that can be seen by the pathologist under the microscope. Once there is cancer arising in the adenoma, the type of the adenoma is not as important as other factors (see below).
12. What is “intramucosal carcinoma” or “carcinoma in situ” or “carcinoma in the lamina propria”?
These changes are also called as high-grade dysplasia. If an adenoma begins to progress toward colon cancer, these are the earliest changes but this early cancer does not yet have the ability to spread to other parts of the body and has probably been caught just in time. While an adenoma with intramucosal carcinoma or carcinoma in situ or carcinoma in the lamina propria needs to be completely removed, it is not the same thing as to what is typically referred to as “colon cancer”, since it cannot spread. Patients who have intramucosal carcinoma or carcinoma in situ or carcinoma in the lamina propria in their adenomas will need to have future colonoscopies at a shorter interval to make sure more polyps do not develop.
13. What if I have invasive adenocarcinoma in an adenoma and it was not entirely removed?
If your adenoma with invasive adenocarcinoma was not completely removed, then you will need another procedure to remove it. While this is most often an operation performed by a surgeon, your treating physician will discuss what therapy options are best for you.
14. What if I have invasive adenocarcinoma in an adenoma and it was entirely removed?
If your adenoma with invasive adenocarcinoma was completely removed you may not require any further surgery if it is not poorly differentiated (see above) and does not have vascular invasion or lymphovascular invasion (see above). You should discuss therapy options with your treating doctor to see what is best for you.

Adapted from material originally produced by Association of Directors of Anatomic and Surgical Pathology (used with permission).
Copyright © 2014 Association of Directors of Anatomic and Surgical Pathology