Ductal dilatation of the breast, also called plasmacytic mastitis, is a sterile inflammatory condition due to ductal obstruction under the areola, causing ductal dilatation, etc., which leads to chemical irritation and immunological response, causing massive plasma cell infiltration. The causes of the pathogenesis of ductal dilatation of the breast are generally the following: 1. Ductal drainage disorders. (1) such as congenital nipple deformity, depression, unclean or foreign hair, fibers, etc. cause blockage of the milk pore, and abnormal duct development can cause ductal narrowing, interruption or occlusion. Poor ductal drainage is often the main cause of the development of the overflow phase to the lump phase. (2) Accumulation of secretions in the ducts, causing ductal dilatation. (3) In some middle-aged and elderly women, the ducts of the breast are degenerative due to ovarian hypofunction, which can lead to the accumulation of secretions in the ducts and ductal dilatation causing the disease. 2, abnormal hormone stimulation: can prompt the duct epithelium to produce abnormal secretion, the duct is obviously dilated. 3, infection: may be related to anaerobic bacterial infection or infection in the areola. Ductal dilatation of the breast is a benign disease of the breast, which is not uncommon in clinical practice and is often misdiagnosed as mastitis, breast tuberculosis or breast cancer due to poor recognition. It can occur at any age, but is more common in young women. It begins with breast pain and a hard lump. If the infection is secondary, the surface skin may become red and swollen, and some patients may have edema and cellulite. The disease can be relieved by anti-infective treatment, but it has a long course and can recur.