The combined pN stage and breast cancer subtypes in breast cancer: a better discriminator of outcome can be used to refine the 8th AJCC staging manual.

pN stage and breast cancer subtypes (BCS) are both well-recognized prognostic indicators. Our previous work has highlighted that patients even with the same pN stage exhibited a significant survival difference in different BCS. Given this achievement, we hypothesized that a statistical interaction might exist between pN stage and BCS. The aim of this retrospective cohort study was to compare the prognostic value of the combined pN stage and BCS (pNnew stage) with either pN stage or BCS alone, and to determine if this combined new stage could serve as an alternative discriminator of outcome.