The short answer
Cancer deposits in lymph nodes are classified by size: isolated tumor cells up to 0.2 mm, micrometastases above 0.2 mm up to 2 mm, and macrometastases larger than 2 mm.
These terms describe the size of cancer deposits found in lymph nodes, measured in millimetres by a pathologist under a microscope.
Isolated tumor cells are clusters no larger than 0.2 mm. The National Cancer Institute records them as pN0(i+), which means no regional node metastasis.
Micrometastases are about 200 cells, larger than 0.2 mm but not larger than 2 mm. They are recorded as pN1mi.
Macrometastases are larger than 2 mm. In breast cancer, the pN1, pN2 and pN3 categories are based on how many nodes are involved.
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The whole article, with every detail and caution.
This page is for people whose pathology report mentions micrometastases, macrometastases, or isolated tumor cells in a lymph node. It explains what the terms measure, how they are recorded, and what they may change.
What these words are measuring
If your report uses the words micrometastasis or macrometastasis, it is describing the size of a cancer deposit found inside a lymph node. Nothing more than that. The pathologist measured the largest cluster of cancer cells in the node and placed it into a category defined by millimeters.
The word metastasis inside these terms is what causes alarm, because in ordinary use it means cancer that has spread to distant organs. Here it is being used in its technical sense — cancer cells that have traveled from where they started — and the distance traveled is to a node beside the tumor.
The size categories
In breast cancer staging, the National Cancer Institute draws two lines, which create three categories.
Isolated tumor cells — clusters no larger than 0.2 mm. Recorded as pN0(i+). Read that notation carefully: it begins with pN0, meaning no regional node metastasis. The (i+) records that something was seen.
Micrometastases — deposits of about 200 cells, larger than 0.2 mm but not larger than 2 mm. Recorded as pN1mi. They fall in the pN1 group, but are recorded separately from larger deposits.
Macrometastases — deposits larger than 2 mm. In breast cancer, pN1 means micrometastases or deposits in one to three axillary (underarm) nodes, pN2 means four to nine nodes, and pN3 means ten or more.
What each category means
Isolated tumor cells are classed pN0(i+), meaning no regional node metastasis. Micrometastases are recorded as pN1mi. Macrometastases are larger deposits, and the number of nodes involved sets the pN category. Ask your care team how your finding affects your stage and outlook.
What they change in practice
That depends on your cancer type, tumor size, grade, biomarker results and what other treatment is planned. The National Cancer Institute says the risk of lymphedema (swelling) goes up with the number of lymph nodes removed, and is lower when only the sentinel node is removed. Your care team will explain whether more node surgery is being considered for you.
A second meaning to be aware of
Outside pathology reports, micrometastasis is sometimes used more loosely for cancer cells too small for any test to find. The two uses are related but not the same. On your report, the word has the precise, measured meaning above.
What to ask your care team
- What size were the deposits, and exactly how are they classified in my report?
- Did the finding change my stage?
- Did it change the treatment recommendation?
- Is any further node surgery being considered?
- If my report says pN0(i+), what does that pN0 mean for me?
Sources
Common questions
Does micrometastasis mean my cancer has spread to my organs?
In the pathology-report sense, no. The word here refers to a very small deposit of cancer cells found inside a lymph node near the tumor, measured in fractions of a millimetre. It is a regional finding recorded under the N category of staging, not a distant metastasis and not stage IV. The word is unfortunately frightening in a way the finding often is not.
Why does 0.2 mm matter so much?
In breast cancer staging, the National Cancer Institute classifies clusters of 0.2 mm or less as isolated tumor cells, written pN0(i+). That means no regional node metastasis. Deposits above 0.2 mm and up to 2 mm are classed as pN1mi.
How are such small deposits even found?
In a sentinel node biopsy, the first lymph node or nodes that a tumor drains into are removed. The National Cancer Institute says a pathologist then checks them for cancer cells. Your report will say how the nodes were examined.
Will micrometastases mean I need more surgery?
Your care team will decide. The National Cancer Institute says the risk of lymphedema (swelling) goes up with the number of lymph nodes removed. What is recommended depends on your cancer type, your other risk factors and what other treatment is planned.
Is the word used differently anywhere else?
Yes, and this causes confusion. Outside pathology reports, micrometastasis is sometimes used loosely for cancer cells too small to find on tests. On your pathology report it has the precise, measured meaning described here.
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Written by: Cancer ExplainedSources last checked: 2026-10-16 what this meansLast updated: 2026-10-16Next planned review: 2027-07-30
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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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