Medical Oncologist
CION Cancer Clinics
What is colon cancer? A plain-language guide | CION Cancer Clinics
Colon cancer is a cancer that starts in the lining of the large bowel, usually from a small polyp that has changed slowly over many years. It is often silent at first, and when it is found early it is very treatable. This page explains where the colon is, how a polyp becomes a cancer, the words you will see on a report, and which page to read next. At CION Cancer Clinics in Hyderabad, our oncologists explain colon cancer in plain words and plan care around you and your family.
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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 colon cancer, in plain words?
Colon cancer is a growth that starts in the lining of the large bowel, the long tube that turns digested food into stool. It almost always begins as a small, harmless-looking bump called a polyp, and over years a few of those polyps change into cancer. Most polyps never do. That slow start is why colon cancer is one of the few cancers that can be found and removed before it causes any trouble.
Where exactly is the colon?
The colon runs up the right side of your belly, across the top, and down the left side, before joining the rectum and the back passage. It is roughly as long as you are tall. Its job is to soak up water and salt from what the small intestine sends it, and to hold stool until you are ready to pass it. Cancer can start anywhere along that length, and where it starts shapes the symptoms you notice.
Why it matters that it starts in the lining
The bowel wall has layers. A cancer that is still in the inner lining is easy to remove. One that has grown through the wall can reach the lymph nodes nearby, and from there the liver or the lungs. How far it has grown is what doctors mean by the stage, and the stage, not the word cancer, decides what treatment is offered.
Colon cancer is not one illness. A polyp with early change and a cancer that has reached the liver carry the same name and very different plans.Four things to know
What should you understand about colon cancer first?
If you read nothing else on this page, read these four cards. They answer the questions families ask us in the first visit.
It grows slowly, from a polyp
Most colon cancers take many years to grow from a polyp into a cancer. That long window is why a colonoscopy, which can remove polyps on the spot, prevents cancer rather than just finding it.
Which means
- A polyp on your report is not a cancer
- Screening works because it catches the polyp stage
It is often silent at first
An early cancer in the colon usually causes nothing you would notice. When symptoms do come they are ordinary ones: a change in bowel habit, blood in the stool, tiredness from a low haemoglobin, a dull ache. Each of these has a benign explanation far more often than a cancer.
It is usually treatable, and often curable
When a cancer is still inside the colon, or has reached only nearby lymph nodes, surgery with or without chemotherapy is given with the aim of removing it completely. Even some cancers that have spread to the liver can be curable if the deposits can be removed.
The stage decides this, and only a tumour board that has seen your scans and pathology can say which stage you are in.It is not the same as rectal cancer
The rectum is the last part of the bowel, and cancer there is treated differently, often with radiation before surgery. If your report says rectum or rectal, you need the rectal cancer hub, not this one.
Not sure whether this applies to you?
Ask an oncologistFrom polyp to cancer
How does a colon cancer actually begin?
A polyp forms in the lining
Cells in the inner lining of the colon divide a little faster than they should and pile up into a small bump. Many adults in middle age have one or more. At this point nothing is wrong with you.
Some polyps slowly change
A polyp of the type called an adenoma can pick up more gene faults over the years. Under the microscope its cells look less and less orderly. Doctors call this dysplasia, meaning disordered growth, and it is still not cancer.
Cancer cells break through
A cancer is declared when those cells push through the thin layer beneath the lining and into the bowel wall. This is the moment a polyp becomes a colon cancer, and it is the moment a colonoscopy is trying to get ahead of.
It grows outward, then travels
Left alone, the cancer grows through the muscle of the bowel wall, then into the lymph nodes that drain it, and later through the blood to the liver or lungs. The whole sequence is explained step by step here.
On your report
What do the words on a colon cancer report mean?
- Polyp
- A small growth on the inside of the bowel. Most are harmless. Only some types, and mainly the larger ones, carry a risk of turning into cancer.
- Adenoma
- The kind of polyp that can become cancer if left for years. Finding one means you should be checked again; it does not mean you have cancer now.
- Adenocarcinoma
- The medical name for nearly every colon cancer. It means a cancer that started in the gland cells of the lining. It is the usual, expected type.
- Biopsy
- A tiny piece of tissue taken during colonoscopy and looked at under a microscope. It is the only way to say for certain whether a growth is cancer.
- Stage
- How far the cancer has grown: still in the wall, into lymph nodes, or to another organ. It is the single fact that decides the treatment plan.
- Colorectal
- A word that lumps colon and rectal cancer together. Many reports and websites use it. The treatment is not the same for the two, so check which part your report names.
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Did you know
Every colon cancer case at CION is discussed at a tumour board, where medical, surgical and radiation oncologists review the scans and the pathology together before a plan is confirmed. The recommendation you receive is not one doctor's opinion.
Being straight with you
What this page cannot tell you
It cannot tell you whether you have colon cancer. Only a colonoscopy with a biopsy can do that, and CION arranges it through an accredited diagnostic partner. If you came here because of a symptom, the honest answer is that most people with blood in the stool or a change in bowel habit do not have cancer, and the only way to settle it is to be examined.
It cannot read your report for you
A pathology or scan report is written for the doctor who ordered it, and the same word can mean different things depending on what sits next to it. If you are holding a report that says adenoma, dysplasia or adenocarcinoma, bring it to an oncologist. Our staging page explains what the stages measure, but it cannot tell you which one you are in.
Who this page is not for
If your report names the rectum, the anus, the appendix or the small intestine, the disease is treated differently and this hub will mislead you. The colon versus rectal page explains why the line is drawn where it is, and the rectal and anal cancer hubs cover their own diseases.
If you are not sure which hub you need, call the helpline with the report in front of you and someone will read the heading with you.Questions we are asked
Common questions about what colon cancer is
Is colon cancer the same as bowel cancer?
Bowel cancer is a looser word that covers both colon and rectal cancer, and British websites use it for both. Colon cancer is the part of that group that starts above the rectum. If a report says bowel cancer, ask which part of the bowel it means.
Is a polyp a cancer?
No. A polyp is a growth that is not cancer. Some kinds can turn into cancer if left for many years, which is why they are removed during colonoscopy and sent to the laboratory. Most people whose polyps are removed never develop colon cancer.
What does colon cancer feel like?
Early on, usually nothing. Later it may cause a change in how often you go, looser or narrower stools, blood mixed in the stool, cramping, bloating or tiredness from a low haemoglobin. Each of these is far more often caused by something ordinary.
Who gets colon cancer?
Mostly people in middle age and older, and most of them have no family history and no single cause. It is being seen more often in younger Indians than it used to be, which is why symptoms in a person in their thirties should not be waved away as piles.
Is colon cancer curable?
Often, yes, when it is found while still inside the bowel or in nearby lymph nodes. Some cancers that have spread to the liver can also be curable if the deposits can be removed. Whether that applies to one person depends on the stage and on the tumour board's review.
How is it diagnosed?
By colonoscopy, where a flexible camera looks at the whole colon and takes a biopsy of anything suspicious. A stool test or a CT scan can raise suspicion, but neither diagnoses cancer. CION arranges the colonoscopy at a partner centre and reviews the result with you.
Does it run in families?
A small share does, through conditions such as Lynch syndrome and polyposis. Having a parent or sibling with colon cancer raises your own risk and usually means starting screening earlier. Most cases, though, arise in people with no affected relative.
What happens after a diagnosis at CION?
Staging scans are arranged, the biopsy is reviewed, and your case goes to the tumour board. You then meet your oncologist to hear the plan in plain language, with the costs written down. If surgery is needed, CION's surgeons plan it and it is carried out at an accredited partner hospital.
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
- American Cancer Society — What Is Colorectal Cancer?
- National Cancer Institute — Colorectal Cancer: Patient Version
- NHS — Bowel cancer
- NHS — Bowel polyps
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
Colon vs colorectal vs bowel cancerThree names you will hear, and when they mean the same thingHow colon cancer develops from a polypThe slow change from polyp to cancer, step by stepColon cancer symptoms: the complete listWhat to watch for, and what is far more often harmlessColon cancer stages explainedWhat the stage measures and why it decides the plan
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Tell us what the report says and where in the bowel it names. An oncologist will explain it plainly and tell you what, if anything, needs to happen next. One helpline serves every CION centre.