Limonene is a major component in the essential oils of citrus fruits. It has demonstrated promising breast cancer preventive and therapeutic effects in preclinical model systems. This goal of this study is to evaluate the distribution of limonene to the breast tissue and its associated biological activities after 2 to 6 weeks of limonene dosing in women with a recent diagnosis of breast carcinoma in situ or atypical ductal hyperplasia scheduled to undergo definitive surgery by conducting an early phase clinical trial. This study will help evaluate the potentials of developing limonene as a breast cancer preventive agent. The long-term goals are to conduct long-term intervention trials to determine the breast cancer preventive activity of d-limonene and to conduct translational clinical research in understanding the effect of d-limonene on arresting/inhibiting/reversing the breast cancer carcinogenesis process. This project was funded by the National Institutes of Health.