Supernumerary breast tissue is ectopic breast tissue that communicates with the breast skin, nipple or areola. Approximately 5.6% of the population exhibits supplementary breast tissue. To date, the National Comprehensive Cancer Network does not provide monitoring and management guidelines for ectopic breast DCIS.

This report describes a woman in her 60’s with a left supernumerary nipple positioned at the inframammary fold with a recently discovered 2-cm palpable anomaly that was confirmed as an intraductal papilloma on histology. Upon surgical excision of the mass, pathology revealed a low grade ductal carcinoma in situ, estrogen receptor positive and progesterone receptor positive. The patient’s case was presented at a multidisciplinary tumor board. She was ultimately recommended for radiation therapy, followed by anti-hormone therapy.