I am currently working on a dataset of electronic health records of patients diagnosed with breast cancer, where one of the features indicates the cancer stage according to the TNM stage:


There is no documentation about this feature unfortunately, so I had to deduce the meaning of each value from the internet.

I was able to retrieve the meaning of most of these stage groups, except one: *U*.

Does anybody know what this code means? I searched online and I could not find an explanation anywhere.


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    If your data set is not documented, you do not have a data set.
    – Bryan Krause
    Feb 21, 2023 at 20:02
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    It's not a legitimate code in any staging system I can find. Therefore, until the people who gave you that list tell you what it means, I'd say all you can do is flag it as an error.
    – Carey Gregory
    Feb 21, 2023 at 22:12
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    @CareyGregory And even doing something simple like excluding those cases as data errors could impact the results of any analyses if the label turns out to be meaningful and not just a random input.
    – Bryan Krause
    Feb 21, 2023 at 22:36
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    @BryanKrause Right, but at least if you flag it the people looking at the output will see that something's wrong and maybe that will motivate them to inform OP what it means. This kind of thing happens a lot in software engineering, actually. End users often imagine that what's obvious to them will be obvious to a programmer who probably isn't a subject matter expert.
    – Carey Gregory
    Feb 21, 2023 at 23:16
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    @CareyGregory Agreed.
    – Bryan Krause
    Feb 21, 2023 at 23:18

1 Answer 1


It has to do with ultrasound staging. See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4482828/

  • 1
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    – Community Bot
    Jul 12, 2023 at 21:31
  • I could not find an isolated major "U" among the abbreviations in that paper - only minor ones in combination, like "uT1" (Table 3) or "uN1" (Table 6), to indicate the staging was done via ultrasound.
    – Arsak
    Sep 7, 2023 at 18:11

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