Breast pain is a symptom that is divided into cyclical breast pain and non-cyclical breast pain depending on whether this symptom is cyclical or not. Periodic breast pain mostly occurs in young women under 35 years old, mostly manifesting as breast swelling and pain before the onset of menstruation, and in more nervous or sensitive patients, a lump may be felt on the breast. In fact, this so-called lump can hardly be described as a lump. There is a saying in Chinese medicine that “if it does not pass, it hurts; if it does not hurt, it passes”, which can explain this phenomenon superficially. From the endocrine point of view, periodic breast pain is related to the cyclical changes of sex hormones. During the endometrial secretion period of the menstrual cycle, the estrogen and progesterone levels in the body are still high (but gradually decreasing), and the effect on the breast is congestion and swelling of the breast, hyperplasia of the epithelial cells of the vesicles, and congestion and edema around the ducts. This change peaks 3-4 days before menstruation, so cyclic breast pain will be most severe just before menstruation. Between the onset of menstruation and about 1 week after menstruation, when both hormones are at lower levels, the changes in the mammary glands during the secretory period are restored and the patient’s symptoms of breast pain are reduced or disappear, resulting in a cycle of symptoms. The duration of cyclic breast pain can be long or short, from one or two days to one or two weeks. Some may also present with axillary and ipsilateral upper extremity pain. Since the outer upper quadrant of the breast is the richest in breast tissue, the most common site of pain is in this area. Strictly speaking, this cyclic breast pain is not considered a disease, except that these symptoms, which may affect the patient’s work, plus the lack of understanding of the substance of this phenomenon, cause a certain amount of psychological stress, and the increasing incidence of breast cancer year by year, as well as the possibility that colleagues, friends and relatives around may suffer from (or talk about) this disease, may even make the patient feel a sense of fear. Non-cyclic breast pain mostly occurs in women in their 40s and is more important than cyclic breast pain. However, most non-cyclic breast pain is due to benign causes, and pain caused by breast cancer accounts for only a very small percentage of non-cyclic breast pain. After the age of 40, women’s ovarian function gradually declines, but this decline, unlike executive management, requires retirement at age. Ovarian decompensation in women is both age-related and varies from person to person. And it cannot be said that non-cyclical breast pain and endocrine are not at all related. Environmental influences, excessive work stress, overwork, trauma, stress or depression, medications and supplements can all cause endocrine disruptions that can lead to breast pain. Most non-cyclic breast pain cannot be considered a disease either, but some patients can have combined cystic breast lesions, breast fibroadenoma, breast ductal dilatation, and intraductal papilloma, etc. Therefore, patients with non-cyclic breast pain should still visit the hospital to except these conditions. In addition, thyroid disease and ovarian disease can also cause endocrine disorders that can lead to breast pain, which also need to be distinguished. In addition to the above mentioned cyclic and non-cyclic breast pain, there is also a type of pseudobreast pain. Pseudobulbar pain is a condition in which the patient presents as “breast pain” but is not actually caused by breast disease. Symptoms such as costochondritis, thrombophlebitis of the chest wall, herpes zoster (especially before the rash), soft tissue trauma to the chest wall, chest or heart disease, cervical spondylosis, and even toothache can all cause symptoms similar to breast pain. These symptoms can be identified by detailed history taking and physical examination, necessary ancillary tests, etc.