Oral contraceptive (OC) use is associated with increased risk of breast cancer for up to 5 years following cessation.9,10,11 In contrast with MHT, associations between OC use and breast cancer risk do not appear to differ by body mass index (BMI).9,12 Previous studies have generally not observed heterogeneity by hormone receptor subtypes12,13,14,15 or by intrinsic subtypes,8,16 although heterogeneity for select associations has been observed. Here, NR4A1 is linked to breast cancer.