Localized ductal dilatation, also known as ductitis or pulpy breast, is a non-bacterial inflammatory condition that is more common during breastfeeding and refers to the enlargement of the glandular lobes of the breast after pregnancy and the consequent expansion of the milk ducts in preparation for the next step of breastfeeding. If it occurs during non-breastfeeding periods, it is considered to be the result of the following conditions: First, it is considered to be a ductal dilatation caused by a ductal tumor of the breast. Secondly, it is considered to be ductitis, which if more severe can cause the ducts to become blocked and dilated. Again, it is considered to be caused by breast enlargement. Lastly, it is considered to be caused by malignant tumor, which requires timely consultation with breast surgery. The etiology of local duct expansion is complex, so if this symptom occurs, it is best to go to a regular hospital for detailed examination in order to exclude malignant tumor.