Kensler KH, et al. - In a subset of Nurses’ Health Study (NHS) and NHSII participants, researchers assessed the PAM50 subtypes (of breast cancer) derived from two preprocessing methods: modified median and subgroup-specific gene centering. They also correlated tumor subtypes by PAM50 with IHC substitutes, as well as, characterized the PAM50 subtype distribution, proliferation scores, and risk of relapse with proliferation and tumor size weighted (ROR-PT) scores in the NHS/NHSII. Findings revealed high comparability of PAM50 subtypes between the two methods. Due to the grouping of Luminal subtypes together, the agreement between tumor subtypes by PAM50 and IHC surrogates improved to fair. Within 5 years, a higher rate of relapse was reported in women with the Basal-like subtype. Poorer outcomes prior to 1999 were noted in HER2-enriched subtypes. PAM50 subtypes for future studies could be derived using either preprocessing method. Most of the NHS/NHSII tumor and tumor-adjacent tissues were divided as Luminal A and Normal-like, respectively.