The short answer
Undifferentiated means the cancer cells look very unlike the normal cells they came from. Anaplastic is a related word. NCI lists undifferentiated as grade 4, a high grade. This page explains both terms and what to ask your care team.
NCI lists undifferentiated as grade 4, which is a high grade.
NCI says a high-grade cancer may grow and spread more quickly.
Grade is not the same as stage. Your care team reads it with the rest of the report.
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This page is for anyone whose pathology report uses the word "undifferentiated" or "anaplastic." It explains what they mean and what to ask your care team.
What undifferentiated means
A pathologist compares tumor cells with the normal cells they came from. The more normal the cells look, the less aggressive the cancer and the more slowly it grows and spreads, says NCI. Undifferentiated cells are the most abnormal-looking group.
What anaplastic means
You may also see the word "anaplastic" in a report or in a cancer's name. Ask your care team what it means for your cancer type.
Where it fits on the grade scale
NCI's grade scale runs from grade 1 (well differentiated, low grade) to grade 4 (undifferentiated, high grade). Grade 3 is poorly differentiated, also high grade.
NCI notes that grading systems can differ depending on the type of cancer. Your report may use a system made for your cancer type.
Grade is one part of the picture
NCI says doctors use grade with other factors to plan treatment and estimate prognosis. A high-grade cancer may grow and spread more quickly and may need more aggressive treatment right away. Grade is not the same as stage. Stage describes tumor size and how far the cancer has spread.
If your report uses these words, ask your care team how the grade fits with your stage and other findings.
Ask these before you leave
- What grade is my tumor?
- What tests will show the stage?
- How does the grade change my treatment options?
Related pages
See What 'Poorly Differentiated' Means, What Does "High Grade" Mean?, and Tumor Grade vs. Stage.
Sources
Common questions
What does undifferentiated mean?
They are tumor cells that look the least like normal cells. NCI lists undifferentiated as grade 4.
Is anaplastic the same as undifferentiated?
They are related terms. Ask your care team which word your report used and what it means for your cancer.
Does a high grade mean the cancer has spread?
No. Grade is how the cells look. Whether cancer has spread is part of staging. Ask your care team about both.
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Sources last checked: 2026-10-02 what this meansLast updated: 2026-10-02Next planned review: 2027-09-27
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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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