The short answer
Colorectal cancer often begins as a small growth called a polyp inside the colon or rectum. Finding and removing polyps can prevent colorectal cancer. Screening tests can help find polyps and colorectal cancer.
Colorectal cancer often begins as a growth called a polyp inside the colon or rectum.
Finding and removing polyps can prevent colorectal cancer.
Screening tests can help detect colorectal cancer and polyps.
Colon cancer and rectal cancer are also described separately.
Subjective: What you might experience
This section describes the symptoms and history a patient might report to their doctor.
Change in bowel habits
diarrhea, constipation, or narrowing of the stool lasting more than a few days.
Blood in or on the stool, or rectal bleeding.
Abdominal cramping, pain, or a feeling that the bowel doesn't empty completely.
Unexplained weight loss, weakness, or fatigue (sometimes from anemia).
Often no symptoms early
many cancers are found through screening.
Risk history
age, family history, inflammatory bowel disease, inherited syndromes, diet and lifestyle factors.
Objective: Tests and findings
Colonoscopy
examines the entire colon and rectum and allows biopsy or polyp removal; the key test.
Biopsy of suspicious areas for tissue diagnosis.
Stool-based screening tests (FIT, stool DNA) as screening tools.
Blood tests including complete blood count and the CEA tumor marker.
CT of the chest, abdomen, and pelvis (and pelvic MRI for rectal cancer) to assess spread.
Interactive anatomy guide
Explore where cancers start and how they are found, on an interactive body map.
Open the anatomy guideAssessment: Staging and prognosis
Diagnosis confirmed by biopsy; most are adenocarcinomas.
Staged with the TNM system based on how deep the tumor grows, node involvement, and metastasis.
Tumor molecular/genetic testing (e.g., KRAS/NRAS/BRAF, MSI/MMR) helps guide therapy.
Rectal versus colon location affects the treatment approach.
Plan: The treatment approach
Surgery to remove the tumor and nearby lymph nodes is the mainstay for localized disease.
Chemotherapy before or after surgery depending on stage.
Rectal cancer often adds radiation or chemoradiation.
Advanced disease
chemotherapy, targeted therapy, or immunotherapy based on molecular markers; clinical trials.
Surveillance colonoscopy, CEA monitoring, and imaging after treatment.
These are simplified, educational SOAP-style summaries showing the kinds of findings clinicians document when evaluating each cancer, based on National Cancer Institute resources. They describe typical diagnostic criteria and workups — not a real patient, and not medical advice. Real clinical notes are individualized. Always rely on your own care team. Based on National Cancer Institute educational content. Educational only — not medical advice.
Common questions
What is a polyp in colorectal cancer?
A polyp is a growth inside the colon or rectum. Colorectal cancer often begins as one of these growths. Finding and removing polyps can prevent colorectal cancer.
Can colorectal cancer be prevented?
In some cases, yes. Colorectal cancer often begins as a polyp, and finding and removing polyps can prevent colorectal cancer. Screening tests are used to detect colorectal cancer and polyps.
What is the difference between colon cancer and rectal cancer?
Colorectal cancer includes cancers of the colon and the rectum. Colon cancer and rectal cancer are also described separately. Your healthcare team can explain which area is involved in a specific case.
Are there tests to find colorectal cancer and polyps?
Yes. Screening tests can be used to detect colorectal cancer and polyps. A healthcare team can explain which options may be right for a person.
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Sources last checked: 2026-07-21 what this meansLast updated: 2026-10-01Next planned review: 2027-07-21
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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