Tumor characteristics and lymph node involvement according to age in the two datasets.

*Data of tumor grade are available in 66.6% subjects in the first dataset and 92.5% in the second dataset.&Immunohistochemical data on ER/PR/HER2 status in the dataset of 2008 is currently being checked and replenished. Only half of values (n = 997, 45.9%) are available. Therefore, the analysis of variable “breast cancer subtype” is not performed in the second dataset.