Following our findings on circulating 27HC and breast cancer risk [8], this exploratory study provides novel data on associations between breast cancer case characteristics and epidemiologic factors and 27HC-related markers in breast tumor tissue, and is the first study on circulating 27HC and breast cancer risk by CYP27A1, CYP7B1, LXR-β, or ERβ tumor markers. This evidence concerns the gene ESR2 and breast neoplasm.