You may be reading this because you’re thinking about getting screened for colon cancer. Maybe you’re waiting for test results. Or perhaps you or someone you care about just learned they have colon cancer.
This guide will help you understand how colon cancer is diagnosed and what your diagnosis means. Learning as much as you can may help you feel ready to talk with doctors about your care.
If you have symptoms of colon cancer, you may have a colonoscopy. If you have a polyp, you’ll have a biopsy to remove the polyp and test it for cancer cells.
Your diagnosis most often will describe where the cancer started, its type, and if it has spread. We use this information to create a care plan just for you.
The most common way to find colon cancer is through a routine cancer screening. Most people with early-stage colon cancer do not have symptoms.
Colon cancer screening can help prevent colon cancer or find it early when it’s easier to treat. Screening guidelines are based on your risk (chances) of getting colon cancer. Talk with your doctor about your risk for getting colon cancer.
MSK recommends people at average risk for colon cancer start getting screened at age 45. We also recommend people at higher risk for colorectal cancer talk with their healthcare provider about when to start screening.
If you’re 75 or older, talk with your healthcare provider about whether screening is right for you. In general, we do not recommend routine screening after age 85.
A colonoscopy is a test that lets your doctor see inside your colon (large intestine). Your doctor will use a colonoscope, a flexible tube with a camera on the end. The images will appear on a video monitor. Watch our video to learn what happens during a colonoscopy.
During your procedure, your doctor can:
Your colon must be empty for your procedure. Your doctor cannot see polyps or other problems if there’s stool (poop) inside your colon. You may need to have the procedure again if this happens. Learn more about colonoscopies.
We use a testing tool developed at MSK called MSK-IMPACT®. It looks at about 500 genes for genetic changes and other tumor traits. Our test finds genetic changes in the tumor that other tests can miss. As of 2024, more than 92,000 of our patients used MSK-IMPACT to find the best treatments for them.
Your doctor may suggest genetic counseling and testing.
Genetic testing is a medical test. It looks at your DNA to see if you were born with certain changes (mutations or variants) in specific sets of genes. These changes raise your chances of getting colorectal and other cancers.
We’ll ask for your written permission to do the test. Before testing, we’ll review your personal and family cancer history to help decide which test is right for you. We’ll explain the test and what the results could mean.
The test involves taking a sample of blood or saliva. You can give a blood sample at an MSK location near you. Or, we’ll mail a saliva kit to your home. The sample is sent to a lab for testing.
When the results come back, often in a few weeks, we’ll go over them with you. If the test shows a gene change that raises your cancer risk, we’ll help you understand what that means. We’ll talk about ways to lower your risk, such as extra screenings or even surgery to prevent cancer.
Hereditary means genes you were born with, passed on from parent to child. A hereditary syndrome can raise your risk for getting colon cancer.
Out of every 100 people with colon cancer, about 5 to 10 of them have changes in certain genes passed from parents to children.
A number of hereditary cancer syndromes, such as Lynch syndrome, are linked to a higher risk for colon cancer.
MSK may offer you genetic testing. It can show if you and your family have hereditary changes (mutations) that raise your cancer risk.
MSK is one of the few hospitals that can test for mutations in many genes at the same time. Our multi-gene panel test can find a hereditary cause of colorectal cancer or polyposis faster. This genetic testing can help us find the best treatment for your type of colon cancer.
MSK’s test can check for gene mutations linked to Lynch syndrome, which can cause colorectal cancer. MSK’s Clinical Genetics Service can do genetic testing for both people with cancer and those at risk for cancer.
MSK will check your biopsy sample for gene changes that affect treatment options.
Our experts are always exploring new ways to diagnose colon cancer and find it early when it’s easier to treat. Explore the latest colon cancer news from MSK.
More young people under age 50, many of them women, are being diagnosed with cancers, such as colorectal cancer.
Learning you have colon cancer can be overwhelming. You’ll hear many medical terms you've never heard before. We’re here to help you understand what they mean and why they matter.
The information in your diagnosis describes important details about the type of colon cancer you have. Your doctors use that information to create the best plan of care for you.
To find out if you have colon cancer, they'll look at a sample of your cells under a microscope. Your doctor collect this sample during a biopsy.
Your cancer diagnosis will include information on the stage of the colon cancer, or how advanced it is. Staging helps us choose a treatment plan. To find the stage of the colon cancer, you'll have diagnostic tests to find out:
Newly diagnosed? Hear advice from our patients.
The cancer stage describes traits such as the tumor’s size, location, and whether it has spread. The stage tells us how advanced the cancer is. The stage helps us choose a treatment that’s best for you. The stage describes which layers of the colon the cancer cells have spread to.
Picture the colon as a tube. Here are the layers of the colon, in order from inside to outside:
When you learn you have colon cancer, you’ll probably have many questions to ask your cancer doctor at your first visit. Talking about treatment options with your doctor can help you feel better prepared to make decisions about your care.
There are a few types of colon cancer. We’re experienced in treating them all, from the most common to the most rare. This information describes each kind of colon cancer and explains how we classify (sort) them.
Most people who are diagnosed with colon cancer have a type called adenocarcinoma (A-deh-noh-KAR-sih-NOH-muh). There are other rarer tumor types too.
Most colon cancers are adenocarcinoma (A-deh-noh-KAR-sih-NOH-muh). This is a cancer that starts in the glandular tissue that lines the colon. This kind of tissue makes mucus and other fluids.
This cancer often starts as polyps that can bleed or cause discomfort. When the polyps grow, they can become painful. They also can change the shape of your stool (poop), making them thin or flat.
Carcinoid (KAR-sih-noyd) tumors in the colon grow slowly. Like adenocarcinomas, they most often start in the small intestine and as polyps in the rectum. Carcinoid tumors are the most common type of neuroendocrine (NOOR-oh-EN-doh-krin) tumor.
Gastrointestinal stromal tumors can be a type of soft tissue sarcoma. They can be anywhere in the gastrointestinal tract but are rare in the colon. These tumors can also be other types of sarcoma that start in the blood vessels or connective tissue of the colon.
Lymphoma is a cancer of the immune system. It more often starts in the lymph nodes but can start in the colon.
The cancer stage describes traits such as the tumor’s size, whether it spread, and where it spread. Staging tells us how advanced the cancer is. The stage guides the choice of treatment.
There are 5 stages of colon cancer, from 0 to 4 (0 to IV). The lower the number, the less the cancer has spread.
Knowing the stage of the cancer helps you and your doctor decide on the best treatment options for you.
Staging describes which layers of the colon the cancer cells have spread to. Picture the colon as a tube. Here are the layers from inside to outside:
N0 means cancer is not in lymph nodes. N1, N2, or N3 means it’s spread to lymph nodes. M0 means cancer has not spread. M1 means it’s spread to distant organs, muscles, or bones.
MSK's Center for Young Onset Colorectal and Gastrointestinal Cancer is the first program of its kind. Our treatment experts work together to care for the needs of young adults with these cancers. We also offer mental health counseling, fertility and sexual health medicine, nutrition, and more.
