Patients with pain in the upper left side of the breasts are considered to have the following reasons: First, consider breast hyperplasia, including menopausal women, estrogen secretion disorders and women’s menstruation due to the rise in the level of estrogen, resulting in physiological breast swelling and pain. The second aspect, consider the patient has mastitis, may be bacteria retrograde upward infection of the mammary gland, or long time not sucking milk, too much milk stagnation and lead to mastitis. The third aspect is to consider that the patient has mammary gland trauma, which includes soft tissue contusion or subcutaneous bruising and edema caused by external impact, as well as undergarment that does not fit properly and causes pain for a long period of time. The fourth aspect is to consider that the patient has breast tumor, which includes malignant and benign tumors, both of which will cause local nerve compression, and malignant tumors will secrete inflammatory factors to stimulate local pain.