The short answer
Isolated tumor cells, or ITCs, are very small clusters of cancer cells found in a lymph node. In breast cancer staging, NCI lists them as clusters 0.2 mm or smaller, recorded as pN0(i+). Micrometastases are larger. This page explains the term and what to ask your care team.
Isolated tumor cells are tiny clusters of cancer cells in a lymph node.
In breast cancer staging, NCI lists ITCs as clusters of 0.2 mm or less, coded pN0(i+).
Micrometastases are larger: more than 0.2 mm up to 2.0 mm, coded pN1mi.
Other cancer types have their own staging rules. Ask your care team what ITCs mean for you.
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This page is for anyone whose pathology report mentions "isolated tumor cells," "ITCs," or "N0(i+)." It explains what they mean and what to ask your care team.
What isolated tumor cells are
When lymph nodes are removed, a pathologist checks them under a microscope for cancer cells. Sometimes only a very small cluster of cancer cells is found. These are called isolated tumor cells.
How they are recorded in breast cancer staging
NCI's breast cancer treatment summary for health professionals uses the AJCC staging tables. In those tables:
- pN0(i+): "ITCs only (malignant cell clusters ≤0.2 mm) in regional lymph node(s)."
- pN1mi: micrometastases, about 200 cells, more than 0.2 mm but no more than 2.0 mm.
So in breast cancer, finding only isolated tumor cells is recorded under N0, with "(i+)" added. Other cancer types have their own staging rules. Ask your care team which rules apply to you.
What this means for you
A lymph node finding is only one part of the stage. The size of the main tumor and whether cancer has spread elsewhere also matter. Your care team uses the whole report to plan next steps.
Ask these before you leave
- Were isolated tumor cells found, and in how many nodes?
- What N category and stage does that give me?
- Does this finding change my treatment options?
Related pages
See Micrometastases vs. Macrometastases, What Does "Positive Lymph Node" Mean?, and What Does N Stage Mean?.
Sources
Common questions
What are isolated tumor cells?
They are very small clusters of cancer cells found in a lymph node. In breast cancer staging, NCI lists them as 0.2 mm or smaller.
What does pN0(i+) mean?
In the breast cancer staging tables NCI uses, pN0(i+) means only isolated tumor cells were found in regional lymph nodes.
How are ITCs different from micrometastases?
Size. In breast cancer staging, micrometastases are more than 0.2 mm up to 2.0 mm and are coded pN1mi.
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Sources last checked: 2026-10-02 what this meansLast updated: 2026-09-27Next 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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