The vague pain inside the left breast is considered to be caused by the following reasons: First, it is considered to be caused by mastocytosis, which mostly occurs in adult women, with hard lumps in the breast, painful sensation and abnormal nipple overflow, which is related to women’s physiological cycle. When the patient’s menstruation is about to come, the pain will be more intense, and the pain will be relieved after the end of the menstruation. Second, consider the left breast inside the mammary inflammation, mostly in women who are breastfeeding, due to the stagnation of breast milk, need to timely empty the stagnant milk. Thirdly, the pain is caused by breast fibroids in the left breast, and may also be caused by other breast diseases such as breast cancer.