Plasmacytoid mastitis, also known as ductal dilatation, acantholytic mastitis, and occlusive mastitis, is a non-bacterial inflammatory disease called “breast leakage” or “nipple fistula” in Chinese medicine. Plasmacytoid mastitis is a rare clinical breast disease, so it is easily misdiagnosed and mistreated. In the chronic stage, nipple overflow, invagination deformity and breast lumps are easily misdiagnosed as breast cancer; in the acute stage, redness, swelling and pain are easily misdiagnosed as bacterial mastitis.