Inflammatory breast cancer in accessory abdominal breast tissue

Accessory breast tissue results from failure of the embryologic mammary ridge, also known as the milk line, to involute. As a result, ectopic breast tissue can develop anywhere along this ridge, which extends from the axilla—the most common location—to the groin. Primary breast cancer in accessory breast tissue is uncommon but has been reported in multiple prior studies. We present a rare case of inflammatory breast cancer presenting in upper abdominal accessory breast tissue in women with a personal history of ipsilateral breast cancer, and highlight the challenges of both diagnosis and treatment of breast cancer in accessory breast tissue.