There are the following possibilities for women with vague pain in the left breast: first, patients should clarify whether they are in the premenstrual cycle, because during this period, due to excessive secretion of estrogen leading to breast enlargement, patients can have vague pain in the breast. Palpation of the local breast can reveal thickening of the breast gland and even nodule formation, and there is obvious local pressure pain. This is a physiological hyperplasia, and the symptoms can be relieved significantly after the end of the menstrual cycle. Secondly, for women aged 30-50, endocrine disorders can lead to an imbalance in the secretion of estrogen and progesterone, causing breast enlargement. At this time, the patient experiences vague pain and gradually worsens symptoms, and needs to be given psychological regulation as well as medication application to achieve better clinical results. Finally, inflammation of the breast can also cause vague pain, especially in breastfeeding women. Mastitis during breastfeeding is prone to these symptoms and has a high incidence, often requiring anti-infective treatment, and can also be caused by trauma and viral infections that lead to intercostal neuralgia.