A Case of Mammary Pagetoid Carcinoma with a Coexisting Fibroadenoma

The patient was a 60-year-old woman who had been undergoing long-term follow-up for Fibroadenoma (FA) of the left breast, which was discovered through Mammography (MMG) for breast cancer screening. She visited our hospital with a principal complaint of erosion of the left nipple. Medical examination was performed, and a rare case of pagetoid carcinoma with coexistence of FA was found. Paget Disease (PD) consists of atypical cells that present in the intraepithelium of the nipple with invasive ductal carcinoma or ductal carcinoma in situ. The Japanese General Rules for Clinical and Pathological Recording of Breast Cancer classifies PD with invasive ductal carcinoma as pagetoid disease and differentiates it from PD with ductal carcinoma in situ. FA is a benign breast tumor that is common in young women. FA does not develop into a malignancy. However, breast cancer cases that occur at the FA epithelium are rarely reported. Based on the Magnetic Resonance Imaging (MRI) findings and pathological diagnosis, the FA had a connection with the invasive ductal carcinoma with an extensive ductal component. Therefore, invasive ductal carcinoma may originate from the FA epithelium.