Medical Oncologist
CION Cancer Clinics
Types of colon cancer: adenocarcinoma and the rarer kinds | CION Cancer Clinics
Almost all colon cancers are adenocarcinomas, which start in the gland cells lining the inside of the bowel. Some adenocarcinomas carry a named subtype, such as mucinous or signet ring cell. Much rarer cancers, including neuroendocrine tumours, lymphoma and GIST, can also start in the colon and are treated differently. This page explains each type, how it is confirmed and what it changes about the plan. 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 types of colon cancer are there?
Almost every colon cancer is an adenocarcinoma. It starts in the gland cells that line the inside of the bowel and make mucus. When a doctor says "colon cancer" without any other word, this is what they mean. A small share of colon cancers are something else entirely, such as a neuroendocrine tumour or a lymphoma, and those are planned differently.
Type, subtype and grade are three separate questions
The type names the cell the cancer started from. The subtype describes how an adenocarcinoma looks under the microscope, for example whether it makes a lot of mucus. The grade says how far the cancer cells have moved away from looking like normal bowel cells. Your report may carry all three, and each one is read alongside the stage.
The newer way of typing a cancer
Doctors now also sort colon cancers by what is happening inside the genes of the tumour. Tests such as MMR and MSI, and RAS and BRAF, divide adenocarcinomas into groups that respond differently to medicines. Two cancers that look identical under the microscope can fall into different groups. This is often more useful for choosing treatment than the microscope label itself.
The type tells you what the cancer is. The stage tells you how far it has gone. You need both before a plan makes sense.The types you may see
Which cancers can start in the colon?
They are listed from the most common to the rarest. The first card covers almost everyone reading this page.
Adenocarcinoma
The usual colon cancer. Most grow slowly out of a polyp over several years, which is why screening and polyp removal prevent so many. It is treated by stage with surgery, and with chemotherapy when the stage calls for it.
Your report may say
- Adenocarcinoma, not otherwise specified
- Well, moderately or poorly differentiated
- Invasive, arising in an adenoma
Mucinous, signet ring and medullary subtypes
These are adenocarcinomas with a distinctive look. A mucinous cancer is made mostly of mucus. In a signet ring cell cancer, mucus pushes each cell's centre to one side so it looks like a ring. Our page on mucinous and signet ring cancer covers both.
They are still treated as colon adenocarcinoma, stage for stage. The subtype adds detail; it does not start a new plan.Neuroendocrine tumours
These start in hormone-making cells scattered through the bowel lining. They range from slow-growing tumours, once called carcinoids, to fast-growing neuroendocrine carcinomas. The grade decides almost everything about how they are treated.
How they differ
- Graded by how fast the cells divide
- Some release hormones that cause flushing or diarrhoea
- Different scans and medicines from adenocarcinoma
The rare ones
Lymphoma of the colon, GIST (a tumour of the bowel's muscle wall), sarcoma and squamous cell cancer can all occur but are uncommon. Each follows its own treatment rules. Our page on rare colon cancers explains them one by one.
Not sure whether this applies to you?
Ask an oncologistFrom biopsy to final report
How is the type of colon cancer worked out?
A biopsy is taken at colonoscopy
Small pieces of the growth are taken during the colonoscopy. CION arranges this at a partner centre. The camera can show that a growth looks suspicious, but only the tissue can say what type it is.
A pathologist reads it under the microscope
The pathologist is the doctor who examines tissue. They name the cell type, any subtype and the grade. For a typical adenocarcinoma this is often clear from the first look.
Special stains settle the unclear cases
When the cells could be one of several types, extra stains are used. They light up proteins that only certain cells carry, which tells an adenocarcinoma apart from a neuroendocrine tumour or a lymphoma.
The tumour's genes are tested
Every colon cancer should have MMR or MSI testing, and RAS and BRAF are tested when medicines depend on them. Our page on universal MMR testing explains why everyone has the first test.
The operation specimen gives the final word
After surgery the whole tumour is examined. The subtype or grade can be refined at this point, and this final report is the one the tumour board uses to plan what comes next.
Side by side
Does the type change the treatment?
What the report says
What it usually means for the plan
Adenocarcinoma
Standard colon cancer treatment, decided by stage
Mucinous or signet ring cell
Same treatment by stage, with a closer look at the lining of the abdomen on scans
Medullary
Treated by stage; often found to be MSI-high on testing
Neuroendocrine tumour or carcinoma
A separate plan built around the grade and spread
Lymphoma or GIST
Mainly medicines, planned by a team that treats those diseases
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Commonly believed
Four things families assume about the type
"Signet ring cancer means nothing can be done."
It is less common and, on average, tends to spread more readily. It is still planned stage by stage with surgery and chemotherapy, exactly like other adenocarcinomas. An average describes a large group of people. It does not describe your father.
"A carcinoid is not a real cancer, so it can be ignored."
Slow-growing neuroendocrine tumours often behave gently, but some do spread, sometimes years later. They need a proper plan and planned follow-up, even when the first operation went well.
"Colon cancer and anal cancer are the same disease."
Anal cancer is usually a squamous cell cancer, a different cell type from colon adenocarcinoma. It is often treated with chemotherapy and radiation rather than surgery first. The two need different specialists and different pages.
"My father's cancer was hereditary, so mine will be a special type."
Inherited colon cancers are still adenocarcinomas. What a family link changes is your risk and how early screening should start. It does not decide what a future cancer would look like under the microscope.
Being straight with you
What this page cannot tell you
It cannot tell you what your own report means for you. The type is one line on a report that also carries the grade, the stage, the margins and the gene results. Read alone, any single line can frighten or reassure the wrong way. Your oncologist reads them together, and that reading is what the plan is built on.
Who this page does not apply to
If the cancer is in the last part of the bowel, inside the pelvis, it is rectal cancer and is often treated with radiation before surgery. See our rectal cancer pages. If it is at the back passage itself, it is usually a squamous cell cancer; see anal cancer. Appendix and small bowel cancers also have their own pages. If your report says adenoma with no cancer in it, that is a polyp report. A removed adenoma is not a cancer diagnosis.
When the type is unclear or unusual
Rare types are easy to misread, and a report can say "suggestive of" when the pathologist was not certain. In that case it is reasonable to ask for the slides to be looked at again before treatment starts. CION can arrange a second review through its pathology partners, and the tumour board will wait for the answer.
If you have a report and are unsure what the type line means, call the helpline. Someone will explain it in plain words, in Telugu if you prefer.Questions we are asked
Common questions about the types of colon cancer
What is the most common type of colon cancer?
Adenocarcinoma, by a very wide margin. It starts in the gland cells of the bowel lining and usually grows out of a polyp. When doctors, websites or treatment guidelines talk about colon cancer, they are almost always talking about adenocarcinoma.
Is adenocarcinoma of the colon the same as colon cancer?
For almost everyone, yes. Adenocarcinoma is the precise name for the usual colon cancer. The word only matters because a few rarer cancers can also start in the colon, and they are named differently because they are treated differently.
What does "moderately differentiated" mean on my report?
It describes the grade. Well differentiated cells still look fairly like normal bowel cells, and poorly differentiated cells look very different. Moderately differentiated sits between the two and is the most common finding. Grade is weighed with the stage; it does not decide treatment on its own.
Is mucinous adenocarcinoma treated differently?
Stage for stage, it is treated the same way as other adenocarcinomas. It is more often found on the right side of the colon and more often MSI-high, which can matter when medicines are chosen. Your oncologist weighs it with the gene results rather than on its own.
Is rectal cancer a type of colon cancer?
The cells are usually the same, adenocarcinoma. But the rectum sits low in the pelvis, close to other organs, so rectal cancer is often treated with radiation before surgery. That is why it is planned separately and has its own pages on this site.
Can the type change after surgery?
The main type rarely changes. The subtype and grade sometimes do, because the pathologist sees the whole tumour rather than a few small pieces. That is why treatment after surgery is planned on the final report, not on the first biopsy.
Is hereditary colon cancer a different type?
No. Cancers caused by Lynch syndrome or polyposis are still adenocarcinomas. What differs is the cause and what it means for relatives. Tumour testing for MMR or MSI is often the first clue that a family should be offered a genetics referral.
Should I get a second opinion on the pathology?
It is worth asking for when the type is rare, when the report uses uncertain words, or when the treatment suggested seems unusual. A second review uses the same slides, so no new biopsy is needed. Call the CION helpline and we can arrange it.
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
- Cancer Research UK — Stages, types and grades of bowel cancer
- American Cancer Society — What Is Colorectal Cancer?
- Cancer Research UK — Neuroendocrine cancers
- National Cancer Institute — Surgical Pathology Reports
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
Adenocarcinoma of the colon explainedThe usual colon cancer, covered in depthNeuroendocrine tumours of the colonIf your report names a neuroendocrine or carcinoid tumourReading your colon biopsy reportEvery line of the report, in plain wordsColon cancer vs rectal cancerWhy the same cell type is treated differently lower down
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