Medical Oncologist
CION Cancer Clinics
The colon cancer diagnostic pathway, step by step | CION Cancer Clinics
The colon cancer diagnostic pathway usually runs in one order: a doctor's assessment, a colonoscopy with biopsy, the pathology report, a staging CT, tissue marker tests and then a tumour board review. Each step depends on the result of the one before. This page walks through every step, who carries it out, where the pathway can branch, and the signs that mean you should not wait for the next appointment. At CION Cancer Clinics, our team goes through your reports with you and plans the next test or treatment step.
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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
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The short answer
What is the diagnostic pathway for colon cancer?
It is the usual order of tests between a first worry and a treatment plan. A doctor assesses you, a colonoscopy finds the growth and takes a biopsy, the pathology report confirms cancer, a CT scan stages it, tissue marker tests are run, and a tumour board agrees the plan. Each step depends on the result of the one before.
Why the order matters
Doing tests out of order wastes time and money. A PET-CT before a biopsy can show something worrying without being able to say what it is. A staging scan booked before anyone has looked inside the bowel may be unnecessary if the growth turns out to be a harmless polyp. Following the order means every test answers a question the last one raised.
Who you will meet along the way
The first doctor is often a physician or general surgeon. A gastroenterologist performs the colonoscopy. A pathologist reads the tissue, and a radiologist reads the scans, though you may never meet either. Then a medical oncologist and a surgical oncologist take over, with the tumour board behind them. Many families in the districts see three or four doctors before reaching an oncologist, and carrying every report to each visit saves repeating tests.
Keep one folder with every report, in date order, and bring it to every appointment.In the order you meet them
What happens at each step of the pathway?
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The first appointment
The doctor asks about your symptoms and family history, examines your abdomen and usually the back passage, and orders a blood count to look for anaemia, a low haemoglobin. A stool test may help decide how urgent the next step is.
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Colonoscopy with biopsy
CION arranges this with a partner gastroenterology team. Samples are taken from anything suspicious, and a small ink mark is often placed beside a growth so a surgeon can find it later.
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The pathology report
The pathologist confirms whether the tissue is cancer, names the type and grades how abnormal the cells look. This is the moment the diagnosis becomes certain.
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Staging scans
A CT of the chest, abdomen and pelvis checks the liver, lungs and lymph nodes. An unclear liver spot may need an MRI, and a PET-CT is kept for specific questions.
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Tissue marker tests
The biopsy tissue is tested for MMR or MSI in every colon cancer, and for RAS and BRAF when the results could change medicine choices. The page on which biomarkers are tested explains each one.
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The tumour board
Oncologists, surgeons, radiologists and pathologists review your scans, reports and general fitness together. The tumour board page explains who sits on it and how a decision is reached.
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The plan conversation
Your oncologist explains the stage, the recommended treatment and why. For most cancers confined to the colon, surgery comes first. The stage stays provisional until the removed bowel has been examined.
Not sure whether this applies to you?
Ask an oncologistWhen the order changes
What if your pathway does not follow the usual order?
Many people reach a diagnosis by a different route. The same questions still get answered, just in a different sequence.
Diagnosed in an emergency
A blocked or burst bowel is treated first, often with an operation at a partner hospital. Biopsy, staging and marker tests are completed afterwards. The page on diagnosis in an emergency admission explains what follows.
Found on a scan for something else
A thickened bowel wall on a scan done for kidney stones or a gall bladder is a question, not a diagnosis. Colonoscopy is still the next step, and many of these turn out to be inflammation or bowel that was simply contracted.
The colonoscopy could not reach the whole colon
A narrowed bowel or a poor bowel preparation can stop the camera short. CT colonography, a scan that builds a picture of the bowel, or a repeat colonoscopy is used to check the rest, sometimes after surgery.
Cancer found in a removed polyp
Sometimes a polyp taken out whole turns out to contain an early cancer. Depending on how deep it reached and how clean the edges are, nothing more may be needed, or surgery may follow. The page on cancer found in a removed polyp covers the choice.
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Signs that should not wait for the next appointment
If you cannot pass stool or wind, your belly is swollen and painful, or you keep vomiting, go to the nearest emergency department today. The same applies to heavy bleeding from the back passage, or bleeding with dizziness or fainting. These can mean a blocked bowel or serious blood loss, and they are treated first. The rest of the pathway can be completed afterwards.
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Who does each step
Where does each part of the pathway happen?
Step
Who carries it out
Consultation and second opinion
CION oncologists, at any CION centre
Colonoscopy and biopsy
A partner gastroenterology team, arranged by CION
Pathology and tissue markers
An accredited partner laboratory
CT, MRI and PET-CT
Diagnostic partners, with images reviewed by the tumour board
Tumour board and treatment plan
CION's multidisciplinary team
Surgery, if needed
Planned by CION's surgical oncologists, carried out at an accredited partner hospital
Being straight with you
What this page cannot tell you
It cannot tell you how long your own pathway will take. That depends on how soon a colonoscopy can be booked, how busy the laboratory is, and whether extra scans are needed. Your doctor can give you a realistic order and a rough timescale once the first results are in.
It cannot tell you your stage
Only the scans and pathology together can do that, and the final stage often waits for the operation. A report that mentions a mass, thickening or a suspicious node is a step on the pathway, not a verdict.
Who this does not apply to
Rectal cancer follows a different pathway. A pelvic MRI is added, and treatment often starts before surgery, so read the rectal cancer pages if your growth is in the rectum. Anal cancer is a separate disease with its own tests. People in a known Lynch syndrome or polyposis family, or on regular colonoscopy surveillance, may have a growth found earlier and follow a plan set by their genetics team.
If you are stuck between two steps and nobody has said what comes next, call the helpline. Someone will look at what you have and tell you the missing piece.Questions we are asked
Common questions about the diagnostic pathway
Can I skip the colonoscopy and just have a scan?
Usually not. A CT can show a mass or spread, but it cannot take tissue or confirm cancer. Colonoscopy also finds small polyps or a second growth elsewhere in the colon. If colonoscopy is unsafe for you, CT colonography may be used and tissue obtained another way.
Why is the CT scan done after the colonoscopy?
Because the colonoscopy decides whether a staging scan is needed at all. When the camera shows a likely tumour, the CT is often booked straight away, so it runs alongside the biopsy rather than waiting for it. If the growth proves harmless, the scan is spared.
Can treatment start before every result is back?
Sometimes. For cancer confined to the colon, an operation can often go ahead before every tissue marker result is in. For cancer that has spread, RAS, BRAF and MMR results usually come first, because they decide which medicines are used. Emergencies are treated straight away.
Is the stage final once the CT is done?
No. The CT gives a clinical stage. After surgery, the pathologist examines the removed bowel and its lymph nodes and gives the pathological stage, which can be higher or lower. That second stage usually decides whether chemotherapy after surgery is advised.
Do I need to repeat tests I had at another hospital?
Often not. Good reports and the actual scan images, on a disc or an online link, can be reviewed as they are. The biopsy slides and tissue blocks can be requested from the laboratory for review or marker testing. Tests are repeated only when they are old, incomplete or unclear.
What should I bring to the first oncology appointment?
Every report in date order: the colonoscopy report with its photographs, the biopsy report, the scan images as well as the written reports, and recent blood tests. Add a list of your medicines and other illnesses such as diabetes. A family member taking notes helps.
Should I get a second opinion before treatment starts?
It is reasonable, particularly before major surgery or when the plan is unclear. A second opinion uses the reports, images and slides you already have, so it should not restart the pathway. CION's oncologists give second opinions at every centre, and the tumour board can review the case.
Who explains the results to me and my family?
The oncologist who will lead your care, usually after the tumour board has met. You should hear the stage, the plan and the reason for it, and which results are still pending. Ask for a written summary you can share with relatives who could not attend.
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
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Sources
- NICE — Suspected cancer: recognition and referral
- NICE — Colorectal cancer
- NHS — Tests and next steps for bowel cancer
- National Cancer Institute — Cancer Staging
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
How colon cancer is diagnosedWhich test answers which question, in more detailHow long does diagnosis take, start to finish?What speeds the pathway up and what slows it downWhat to ask at your diagnosis appointmentQuestions to take into the plan conversationColon cancer stages explainedWhat the staging result means once you have it
Talk to us
Stuck between tests and not sure what comes next?
Tell us which step you have reached and send the reports you have. A CION oncologist will say what is still needed and help arrange it through our partners. One helpline serves every CION centre.