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:
*U*, 0, I, IA, IB, IIA, IIB, III, IIIA, IIIB. IIIC, IIINOS, IV, and UNK.
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.
Thanks!