NCCN Guidelines for Patients
Colon Cancer, Version 1.2017
Cancer cell tests
Tissue removed from your body will be sent to a
pathologist. This may be tissue from a biopsy or
surgery. The pathologist will examine the samples
using a microscope.
The pathologist will study the parts of the cells to
classify any disease. This is called histologic typing.
When cancer is found, he or she will do other tests to
learn more about the cancer.
One important test result is the cancer grade. The
cancer grade is a score assigned by the pathologist.
He or she will rate the cancer based on how the
cancer cells look. The score is a sign of how fast the
cancer will likely grow and spread. Higher scores
mean that the cancer will likely grow and spread fast.
All lab results are recorded in a pathology report.
A report will be written each time tissue is removed
from your body and tested for cancer. These reports
are vital to planning treatment.
Review your pathology report(s) with your doctor. Ask
questions if you don’t understand. This information
can be complex. It’s also a good idea to get a copy of
your pathology report(s) and take notes.
Not all colon cancer cells are alike. Cancer cells can
differ by which genes have mutations. Some gene
mutations are known to have an effect on cancer
treatment. Molecular testing includes tests of genes
or their products (proteins). Molecular testing that is
advised for colon cancer is described next.
RAS is a family of proteins found in cells. Some
colon cancers have abnormal genes that control
the RAS proteins. As a result, the RAS proteins are
overactive and promote cancer cell growth. Some
treatments for metastatic colon cancer do not work
genes are abnormal. Thus, testing for
genes is advised for
The BRAF V600E mutation is also known to affect
some treatments. About 5 to 9 out of every 100 colon
cancers have a mutated
gene. Testing for
mutation is advised for metastatic
MMR and MSI
Normal MMR (
epair) proteins correct
DNA errors that occur when copies of DNA are
being made. In some colon cancers, MMR mutations
cause one or more MMR proteins to be absent. As a
result, DNA errors aren’t corrected and the number
of gene mutations increases. Doctors call this dMMR
The DNA errors caused by dMMR often occur in
microsatellites. Microsatellites are a tiny part of the
DNA code that is repeated many times in a row.
See Figure 8.
Due to dMMR, microsatellites may
be shorter or longer than normal. This is called MSI
Loss of MMR proteins and MSI are features of Lynch
syndrome. One or both features is present in over
90 of every 100 Lynch syndrome-related cancers
(>90%). However, these features can still occur in the
absence of Lynch syndrome. They are found in about
15 out of every 100 colon cancers (15%) without
Testing for loss of MMR proteins or MSI is advised
for all people with colon or rectal cancer. These
features may affect your treatment plan. There are
two tests that can be done.
eaction) is a test that can
assess for MSI. The test consists of a process in
Cancer cell tests