Medical Oncologist
CION Cancer Clinics
What tests will I need for colon cancer? | CION Cancer Clinics
Most people checked for colon cancer need four kinds of test. A colonoscopy with a biopsy confirms or rules it out. A CT scan of the chest, abdomen and pelvis shows whether it has spread. Blood tests and tests on the tumour tissue then guide treatment. This page lists each one, the question it answers, and what each result leads to next. At CION Cancer Clinics, our team goes through your reports with you and plans the next test or treatment step.
NG
Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed October 2026, next review due October 2027
17+specialists on panel
15,000+patients treated
35+centres across Telangana & AP
4.8★ / 800+Google rating
On this page
The short answer
Which tests are used to diagnose colon cancer?
Most people need four kinds of test. A colonoscopy, a camera test of the large bowel, with a biopsy shows whether there is cancer. A CT scan of the chest, abdomen and pelvis shows whether it has spread. Blood tests show how your body is coping, and tests on the biopsy tissue show what kind of cancer it is.
Only one of them can confirm cancer
The biopsy is the only test that gives a diagnosis. A biopsy is a few small pieces of tissue, looked at under a microscope by a pathologist. A scan can show a thickened bowel wall and a blood test can come back raised, but neither proves cancer. That is why doctors insist on tissue even when the picture looks obvious. Our page on a diagnostic colonoscopy explains what that day involves.
The order matters more than the list
Tests come in a sequence because each result decides the next step. Rushing to a PET-CT before the biopsy, or repeating a CT done elsewhere a few days ago, adds cost and delay without adding answers. Bring every report, scan CD and slide you already have to the first appointment.
A positive stool test or a raised blood marker is a reason to look further. Neither one is a diagnosis.Four questions, four tests
What does each test actually tell the doctor?
Every test on the list is there to answer one question. Once you know the question, the list stops feeling random.
Is it cancer? Colonoscopy and biopsy
A thin camera looks at the whole lining of the colon, and samples are taken from anything abnormal. CION arranges the colonoscopy at an accredited partner hospital, and the tissue goes to a pathology laboratory.
It answers
- Whether there is cancer at all
- Where in the colon it sits
- Whether there are other polyps
Has it spread? The staging CT scan
A CT of the chest, abdomen and pelvis checks the liver, lungs and lymph nodes, the places colon cancer most often travels to. It is the main staging scan for almost everyone. Our page on why all three regions are scanned explains the reasoning.
How is your body coping? Blood tests
A full blood count looks for anaemia, a low haemoglobin, which is common when a tumour has bled slowly for months. Liver and kidney tests check that your body can handle surgery and medicines. A CEA blood test records a starting value to compare against later.
What kind of cancer? Tests on the tissue
The biopsy is checked for MMR or MSI, two ways of testing whether the tumour's DNA repair system works. For cancer that has spread, RAS and BRAF gene tests help choose the right medicine.
These use tissue already taken. They do not need a new procedure.Not sure whether this applies to you?
Ask an oncologistResult by result
What does each result lead to next?
-
A symptom or a positive stool test
Bleeding, a lasting change in bowel habit, anaemia or a positive FIT result leads to a colonoscopy. A stool test only shows that blood is present. It cannot say why, so it is never a diagnosis.
-
The colonoscopy finds a growth
Biopsies are taken, and the spot may be marked with a small ink tattoo so a surgeon can find it later. The result takes longer than the procedure itself. Ask the unit when to expect it.
-
The biopsy confirms cancer
The staging CT and blood tests follow, often in the same stretch of appointments. MMR or MSI testing is requested on the same biopsy, so nothing needs to be taken again.
-
The CT is clear, or something is unclear
If nothing shows beyond the colon, the plan usually moves toward surgery. If a spot in the liver or lungs cannot be called, an MRI of the liver or, in selected cases, a PET-CT is added to settle it.
-
The tumour board meets
Surgeons, medical oncologists, radiologists and pathologists review every result together. At CION the plan is agreed at that meeting, before treatment begins, so no single test drives the decision.
On your reports
What do the words on the test reports mean?
- Histopathology
- The microscope report on your biopsy. This is the document that confirms or rules out cancer.
- Adenocarcinoma
- The commonest type of colon cancer. It starts in the gland cells that line the inside of the bowel.
- Staging
- Working out how deep the cancer has grown and whether it has spread. The stage guides which treatment is offered.
- CEA
- A protein some colon cancers release into the blood. Useful for tracking a known cancer, not for finding one.
- Lymph node
- A small bean-shaped gland that filters fluid from the bowel. Cancer in the nodes changes the stage and the plan.
- Lesion
- Any abnormal area. It is a neutral word and does not mean cancer on its own.
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
Commonly believed
Can a blood test or a scan alone diagnose colon cancer?
"A CEA blood test will show whether I have colon cancer."
Many people with colon cancer have a normal CEA, and smoking, liver disease and inflammation can raise it in people without cancer. It is used to follow a known cancer, never to diagnose one.
"My CT scan was normal, so I do not need a colonoscopy."
A routine CT can miss small or flat growths in the bowel wall, and it cannot take tissue. If you have symptoms, colonoscopy is still the test that answers the question.
"Taking a biopsy will make the cancer spread."
There is no good evidence that a biopsy taken during colonoscopy spreads colon cancer. Without it, no surgeon or oncologist can plan treatment safely.
"More tests always means better care."
Each test should answer a question the earlier ones left open. A PET-CT for everyone, or the same scan repeated at different hospitals, adds cost and waiting without changing the plan.
Being straight with you
What this page cannot tell you
It cannot tell you which tests you personally need. That depends on your symptoms, your general health, what has already been done and what the first results show. The oncologist reviewing your reports decides, and the list can change as answers come in.
Who this list does not fit
If you are well and being screened, the pathway starts with a stool test or a screening colonoscopy, and most of this page does not apply yet. If the tumour is in the rectum, the last part of the bowel, you will also need an MRI of the pelvis, and the rectal cancer pages are the right place. If you were diagnosed during an emergency operation, many of these tests happen after surgery rather than before.
It cannot read your report for you
The same phrase can mean different things depending on what sits around it. If you are holding a biopsy or CT report you do not understand, bring it to a specialist rather than searching it line by line late at night.
Already have reports from another hospital? Bring the scan images as well as the written reports, so nothing is repeated without a reason.Questions we are asked
Common questions about colon cancer tests
Which test confirms colon cancer?
Only a biopsy, examined under a microscope by a pathologist. It is usually taken during colonoscopy. Scans, blood tests and stool tests can raise suspicion, and they help with staging, but none of them can prove that a growth is cancer.
Do I need a PET-CT scan?
Most people do not. A CT of the chest, abdomen and pelvis is the standard staging scan. A PET-CT is added when the CT shows something that cannot be called either way, or when surgery for spread to the liver or lungs is being considered.
Will I need an MRI?
Not always. An MRI of the liver helps when a spot on the CT cannot be clearly called harmless or cancer. An MRI of the pelvis is routine for rectal cancer, which is treated differently, but it is not routine for cancer higher up in the colon.
Why is my blood being tested so many times?
Each sample answers something different: haemoglobin, liver and kidney function, clotting before a procedure, and the starting CEA. Some are repeated before each procedure or treatment because results change. Asking which tests are being done, and why, is a perfectly reasonable question.
What if the colonoscopy could not go all the way round?
Then part of the colon has not been seen. The doctor may repeat the colonoscopy after better bowel preparation, or arrange a CT colonography, a scan that builds a picture of the bowel. The unseen part must be checked before any operation is planned.
Are MMR and MSI tests a separate procedure?
No. They are done on the biopsy tissue already taken, or on the tumour removed at surgery. A result showing the repair system is not working can point to Lynch syndrome, an inherited condition, so the team may suggest a genetics referral for you and your family.
Can tests done at another hospital be used?
Usually, yes. Recent good-quality CT scans and biopsy reports can often be reviewed rather than repeated. Bring the actual scan images on a CD or link, not just the written report, and the biopsy slides or blocks if the pathologist asks for them.
How do I know the tests are finished?
When the tumour board has reviewed all the results and your doctor explains a treatment plan. Until then, more tests may be added as answers come in. Call the CION helpline if you are unsure what is still pending or why a test was ordered.
Your Specialists
Meet CION's colon cancer specialists. Bring your colonoscopy, scan or biopsy report.
Our surgical and medical oncologists plan colon cancer care together: which operation, whether chemotherapy is needed, and the follow-up that comes after.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
Want a specific doctor for your case? Mention them when booking.
Book Free ConsultationBook an appointment with our specialist
Share your name and number — we'll call you back within 30 minutes to schedule your consultation.
Sources
- NHS — Tests and next steps for bowel cancer
- American Cancer Society — Testing for Colorectal Cancer
- Cancer Research UK — Diagnosing bowel cancer
- National Cancer Institute — Tumor Marker Tests in Common Use
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
The diagnostic pathway step by stepThe same tests laid out in the order they happenReading your colon biopsy reportWhat the words on the most important report meanHow long does diagnosis take?What to expect between the first test and a planCost of diagnosis and stagingIndicative Hyderabad costs for each of these tests
Talk to us
Not sure which tests you still need?
Share the reports you already have and we will tell you what is missing and what does not need repeating. One helpline serves every CION centre.