Types of colorectal cancer: common, rare, and what to know

Looking for a clear, human explanation of colorectal cancer types? You're in the right place. Here's the short version: about 95% are adenocarcinomas that often start as tiny polyps. The rest are rare colon cancerslike neuroendocrine tumors, lymphomas, sarcomas, and very uncommon squamous cell and melanoma cases. Different types can behave differently, which matters for symptoms, tests, and treatment choices.

Below, I'll walk you through the major colorectal tumor types, the colon cancer signs to watch for, how doctors figure out what's going on, and what treatment paths often look likeso you can move from worry to a plan. I'll keep it friendly, plain-language, and practical. If anything sparks questions, jot them down. Your curiosity is your superpower here.

Quick overview

When people say "colorectal cancer types," they might mean a few things: where the tumor is (colon versus rectum), what kind of cell it came from (for example, a gland-forming cell versus a nerve-like cell), and how it looks under the microscope. Each layer tells your care team something important.

Colon vs. rectal

Is the type different just because of location? Not exactlythe most common type (adenocarcinoma) can grow in both places. But the care often changes with location. The rectum sits in a tight space with nerves and nearby organs, so rectal cancer treatment may involve radiation before surgery, while many colon cancers go straight to surgery first. Surgeons also think about preserving bowel function and continence, which can shape decisions. As experts at leading centers note, the anatomy around the rectum and the option of pre-surgery radiation often create distinct paths for care compared with colon tumors.

How types are named

Doctors name colorectal cancer types by the cell of origin (like gland cells for adenocarcinoma or hormone-producing cells for neuroendocrine tumors), by histology (what it looks like under the microscope), and by grade (how aggressive the cells appear). A quick checkpoint many folks mix up:

Type = the kind of cell it started from. Grade = how abnormal and fast-growing it looks. Stage = how far it has spread. Think of type as "what," grade as "how intense," and stage as "how far."

Common type

Let's start with the big one: adenocarcinoma. If you or someone you love has colorectal cancer, odds are high this is it.

What is adenocarcinoma?

Adenocarcinoma begins in the gland cells that line the inside of the colon and rectumthe cells that make mucus to help things move along smoothly. Most of the time, it starts as a small growth called a polyp. Not all polyps are dangerous, but some can turn into cancer over years.

From polyp to cancer (and why colonoscopy matters)

Picture a polyp as a tiny bump on the wall of a long tunnel. Over time, some polyps become adenomas (precancerous), and a fraction of those can transform into cancer. Colonoscopy lets doctors see and remove polyps earlybefore they become trouble. It's like fixing a tiny pothole before it becomes a crater.

Adenocarcinoma symptoms

Early on, there might be no symptoms at allthat's why screening is such a lifesaver. When symptoms do show up, they can include blood in the stool, a change in bowel habits (more frequent, less frequent, or not feeling "finished"), thinner stools, cramping or abdominal pain, fatigue, and unexplained weight loss. If you've noticed any of these, it's absolutely worth a call to your doctor.

Colon vs. rectal signs

Overlaps are common, but colon cancers may show up as iron-deficiency anemia or vague abdominal discomfort, while rectal cancers can cause a feeling of urgency, mucus in stool, or pain with bowel movements. Bright red blood is more often noticed with rectal tumors, though any bleeding deserves attention.

Subtypes that matter

Under the adenocarcinoma umbrella, two subtypes can influence prognosis and treatment decisions:

Mucinous adenocarcinoma: These tumors produce a lot of mucus (you can think of it like a jelly-like component), which can alter how they behave and respond. They make up about 1015% of adenocarcinomas.

Signet ring cell adenocarcinoma: Less than 1% of cases. Cells look like they have tiny signet rings inside. These tend to be more aggressive and may be diagnosed at a more advanced stage.

How doctors diagnose it

Diagnosis usually starts with a colonoscopy to visualize the tumor and remove or biopsy tissue. Pathologists confirm the type by looking at cells under a microscope. Imaging such as CT or MRI helps see if it has spread. Blood tests can check for anemia and sometimes track tumor markers, but biopsy is what provides the definitive answer. Each test answers a different question: "What is it?" "Where is it?" and "How far has it gone?"

Treatment options

For most colon adenocarcinomas, surgery to remove the tumor and nearby lymph nodes is the first step. If the cancer is more advanced or at higher risk of returning, chemotherapy may follow. For rectal cancer, it's common to have chemotherapy and radiation before surgery to shrink the tumor and lower the chance of recurrence. Targeted therapies (which home in on specific mutations) and immunotherapy can be powerful in certain cases, especially when the tumor has specific biomarkers like MSI-H or dMMR.

Rare types

Now for the other side of the story: rare colorectal tumor types. They're uncommon, but knowing they exist matters because their treatments can be quite different from standard adenocarcinoma approaches.

Neuroendocrine tumors

Neuroendocrine tumors (NETs) start in hormone-producing cells and can be slow-growing or fast-growing. Slow ones (NETs) may cause subtle symptoms or none at all; faster ones (neuroendocrine carcinomas, NECs) behave more aggressively. Some NETs release hormones that cause flushing, diarrhea, wheezing, or a racing heartbeat. Diagnosis can involve endoscopy, biopsy, imaging like CT/MRI or special scans, and blood or urine biomarkers (for example, chromogranin A).

Treatments range from surgery for localized tumors to somatostatin analogs that calm hormone symptoms and slow growth. Depending on the case, radiation, chemotherapy, targeted therapy, or peptide receptor radionuclide therapy (PRRT) might be used.

Primary colorectal lymphoma

Lymphomas start in the immune system cells. When they arise in the colon or rectum, symptoms can mimic everyday gut issuesabdominal pain, changes in bowel habits, or weight loss. Because lymphoma isn't an adenocarcinoma, treatment usually leans on systemic therapy (chemotherapy, sometimes with radiation), with surgery used selectivelyfor diagnosis, complications, or very localized disease.

GIST tumors

Gastrointestinal stromal tumors (GIST) arise from the interstitial cells of Cajalthe "pacemaker" cells of the gut. They can bleed, causing black stools or anemia, and sometimes cause pain or fullness. These tumors often respond to targeted therapies called tyrosine kinase inhibitors (TKIs), especially when they carry specific mutations. Surgery is common for localized GIST, with TKIs used before or after to shrink or control disease.

Leiomyosarcoma

Leiomyosarcoma is a smooth muscle sarcomathink of it as cancer from the muscle layer of the bowel wall. It's rare and may be silent early on. Surgery is the mainstay when possible. Chemotherapy or radiation may be considered depending on stage and location, but decisions are individualized and often guided by sarcoma specialists.

Colorectal melanoma

Melanoma in the colon or rectum is very rare and can be either a primary tumor (starting there) or a metastasis from melanoma elsewhere on the skin or eye. The workup focuses on finding the true origin because that changes the plan. Immunotherapy has transformed melanoma care and is often considered when appropriate.

Squamous cell carcinoma

Squamous cell carcinoma rarely starts in the colon or rectum. When it does, treatments aren't as standardized and often depend on whether the tumor truly started there or arrived from another site. A careful diagnostic process is key to choosing the right path.

Genetic syndromes

Some people inherit changes in certain genes that raise the risk of colorectal cancer typesand sometimes shift which type occurs and at what age. If your family tree has multiple relatives with colon or rectal cancer (especially at younger ages), or related cancers like uterine cancer, a genetics conversation can be empowering.

Lynch syndrome

Lynch syndrome is the most common inherited colorectal cancer syndrome. It involves mismatch repair (MMR) genes, which normally fix DNA mistakes. When MMR is broken, tumors can develop earlier and sometimes in multiple locations. These tumors are often MSI-H or dMMRlabels that matter because they can respond beautifully to immunotherapy in advanced settings. People with Lynch usually start screening earlier and more often.

Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) leads to hundreds of polyps in the colonsometimes starting in adolescence. Without management, the chance of developing colorectal cancer is extremely high. Care involves early and frequent colonoscopies, and sometimes prophylactic surgery to remove part or all of the colon. It's a lot to process, but proactive care saves lives.

Peutz-Jeghers and others

Other syndromeslike Peutz-Jegherscarry risks for multiple cancer types and may show up as distinctive polyps or freckle-like spots on the lips or mouth. If any of this sounds familiar, genetic counseling can help map out screening steps for you and, if needed, for family members too.

Symptoms checklist

Let's put the most common colon cancer signs in one place. If you've noticed one or more of these, take note of how long they've been around and how they're changing:

Common signs

Blood in or on your stool (bright red or dark), unexplained changes in bowel habits (new constipation, diarrhea, or going more or less often), thinner "pencil" stools, belly cramping that sticks around, unexplained weight loss, fatigue, and signs of anemia (shortness of breath climbing stairs, unusual tiredness).

By tumor type

Some patterns point toward specific colorectal tumor types: flushing and watery diarrhea without a clear cause can hint at hormone-producing NETs; persistent, worsening crampy pain and bowel obstruction symptoms (nausea, vomiting, not passing gas) can occur with adenocarcinoma; unexplained anemia and black stools may raise suspicion for GIST. None of these are diagnosesnot even closebut they tell your clinician which tests to prioritize.

Urgent red flags

Severe abdominal pain with vomiting, black tarry stools with lightheadedness, bleeding that won't stop, or sudden belly swellingthese are reasons to seek urgent care now. Trust your instincts. If something feels off, it's worth checking.

Diagnosis path

What happens from "I'm worried" to "I have answers"? Here's the typical path, step by step.

Screening to biopsy

Screening options include stool-based tests (like the FIT test or stool DNA tests) and colonoscopy. A positive stool test means it's time for a colonoscopy to look directly and remove or sample anything suspicious. Polyps are often removed right away. If a mass is found, a biopsy is taken to determine the type.

Imaging and labs

Depending on what's suspected, you might have CT scans, MRI (especially for rectal cancers), or endoscopic ultrasound for more detailed views. Some rare types use biomarker testsfor example, chromogranin A for certain NETs. For all adenocarcinomas, it's standard to test the tumor for MMR or MSI status, because that result can open the door to immunotherapy if needed. Molecular profiling may look for RAS, BRAF, HER2, or NTRK changes to guide targeted therapies.

Pathology report

Your pathology report pulls together the essentials: histology (type), grade (how aggressive it looks), margins (did surgery remove all visible tumor), lymph node status, and molecular findings. It's a lot of jargon. Don't hesitate to ask your care team to translate every line. A good rule: if you can explain your report in your own words, you're ready to make decisions with confidence.

Treatment basics

Treatment depends on both the colorectal cancer type and the stage. The goal might be cure, long-term control, or relief of symptomsoften, it's a combination over time.

Localized disease

Very early cancers can sometimes be removed endoscopically during colonoscopy. For larger or deeper tumors, surgeons remove the involved bowel segment and nearby lymph nodes. With rectal cancers, chemotherapy and radiation before surgery can shrink the tumor, lower recurrence risk, and sometimes allow less invasive surgery. Recovery plans also focus on bowel function, continence, and quality of life.

Advanced or metastatic

When cancer has spread to lymph nodes or distant organs, systemic therapy steps in. Chemotherapy backbones (like FOLFOX or FOLFIRI) are common starting points. Targeted therapies are added or chosen based on mutations (for example, anti-EGFR therapy if RAS wild-type; BRAF-directed combinations for BRAF V600E; HER2-directed therapy for HER2-positive). For MSI-H or dMMR tumors, immunotherapy can be a game-changer. Local treatments (like surgery or ablation) may still play a role, especially for limited liver or lung metastases.

Rare type pathways

Different rules apply for rare colon cancers. NETs may respond to somatostatin analogs, PRRT, or targeted agents. GIST tumors are often treated with TKIs tailored to their mutations. Lymphomas follow hematology-oncology protocols, usually chemo-first. Melanoma in the bowel often involves immunotherapy. Sarcomas are best managed with sarcoma-experienced teams, with surgery at the center and selective use of chemo or radiation.

Balancing benefits and risks

Treatments can bring side effectsnausea, fatigue, neuropathy, bowel changes, fertility concerns, and sometimes the possibility of a temporary or permanent ostomy. These aren't just medical details; they're day-to-day realities. Ask your team about ways to protect your nerves during chemo, pelvic floor therapy after rectal treatment, nutrition support, exercise programs, and mental health resources. Shared decision-making means your values sit at the table, not just your lab results.

Screening and prevention

If there's one practical takeaway I hope stays with you, it's this: screening can catch problems while they're still tinyand easier to treat. For most people at average risk, screening starts at age 45. If you have a strong family history or a genetic syndrome, you'll likely start earlier.

Who and when

Average-risk adults begin at 45 and continue regularly through 75, with individual decisions beyond that based on health and history. If a parent or sibling had colorectal cancer (especially under age 60), ask your clinician about starting earlieroften at 40 or ten years younger than the family member's diagnosis age.

Test options

There's no one-size-fits-all. Stool-based tests like FIT are noninvasive and done at homegreat for people who want a simple start, but they must be repeated on schedule and followed by colonoscopy if positive. Stool DNA tests are another at-home option. Colonoscopy is less frequent but requires prep and sedation. The best test is the one you'll actually do on time. If you love checklists, make one: due date, reminders, ride homedone.

Lifestyle steps

We can't lifestyle our way out of every risk, but small, steady changes help. Aim for a plant-forward diet with fiber, limit processed meats, keep alcohol modest, move your body most days, don't smoke, and maintain a healthy weight. Think of it like tending a garden: sunlight, water, and regular care. Progress beats perfection.

Helpful notes

If you're the kind of person who likes to double-check facts (I see you!), organizations like the American Cancer Society and Cancer Research UK offer reliable, easy-to-read guides that align with what we've covered here. For example, the American Cancer Society explains staging, screening, and treatment choices in depth according to their colon and rectal cancer overview, and Cancer Research UK dives into histology and grading in their types of bowel cancer pages. If you're curious about screening ages and intervals, guidance aligns with recommendations described in USPSTF colorectal screening recommendations.

Bringing it together

Understanding colorectal cancer types helps you match symptoms, testing, and treatment with what's most likelyand not miss the rare conditions that need different care. Most cases are adenocarcinomas starting from polyps, which screening can catch early. Rare colon cancerslike NETs, lymphomas, GISTs, sarcomas, melanoma, and squamous cell carcinomaare uncommon but important because their treatments and outlooks differ.

If you've noticed new bowel changes, bleeding, or unexplained fatigue, talk to your clinician. And if you're 45 or older, consider screeningeven without symptoms. Have a family history or a genetic syndrome? Ask about earlier testing. What worries do you want answered at your next appointment? Write them down now while they're top of mind. And if you'd like, I can help you map out questions for your doctor or sketch a personalized screening plan to fit your life.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.