Gram IT, et al. - Researchers examined whether the higher risk of smoking-related breast cancer was similar for five racial/ethnic groups in the Multiethnic Cohort (MEC) study and estrogen (ER) and by progesterone (PR) receptor status. Study participants included 67,313 women enrolled in the MEC study at 45-75 years of age who were followed from 1993 to 2013. Breast cancer cases and tumor receptor status were identified via linkage to the Hawaii and California Surveillance, Epidemiology and End Results Program cancer registries through December 2013. In all, 4,230 incident, invasive breast cancer cases were identified during a mean follow-up of 16.7 years. They discovered that the increased risk of smoking-related breast cancer in racial/ethnic groups and by ER and PR status is similar, indicating that breast cancer should be considered as a smoking-related cancer.