At present, more than 90% of breast cancer patients are diagnosed through screening by doctors after occasional detection of breast lumps by themselves. Due to the lack of awareness of cancer prevention among most women and the low prevalence of breast self-examination, about 2/3 of the breast cancer cases treated clinically are still in the middle or late stage. Therefore, breast self-examination knowledge should be promoted and popularized. Married adult women, especially those over 30 years old, should actively perform breast self-examination. The examination should be done at a constant time, usually within 2 weeks after each menstrual period, so that it is the time when the breast glands are at their loosest and least painful to touch (due to ovarian function). For those who have stopped menstruating or had their ovaries removed due to other problems, the examination can be done on a fixed day each month. A detailed record of each examination should be kept, and if necessary, a self-examination diary should be kept to serve as a control. During the examination, the upper half of the body should be completely naked, sit upright or in front of a dressing mirror, face the mirror and compare and observe both breasts, carefully observe whether the contour of each part of the breast is symmetrical, whether the size has changed, whether there is redness, swelling, bulging and skin changes, etc.; observe whether there are changes in the nipples, such as sunken, upturned, retracted and so on. Then raise your head and chest, and put your palms in front of your chest to confront or put your hands on your waist to do chest expansion exercise, so that the pectoralis major muscle is tense and then compare the shape of the breasts. In addition, when changing undergarments, attention is paid to the front area of the nipple for signs of contamination (caused by nipple overflow). After the end of the breast visualization, breast palpation, the steps are: ① lying flat on the bed, with a thin pillow slightly cushion the shoulder of the examined side, the upper limb of the examined side overhead, the examination side fingers together, flat on the surface of the opposite side of the breast, using the palm side of the fingertips gently touch the various parts of the breast. The order of touching is usually external up → internal up → internal down → external down, and finally check the central area, while paying attention to touching the axilla. This is repeated 3 times. ②Gently push your fingers from around the breast to the nipple area, and finally gently squeeze the nipple areola to observe if there is any fluid overflowing from the nipple. ③ For large sagging breasts, you can take a bending and flexing position to let the breast sag, then hold the breast with one hand and touch it with the other. It is forbidden to grasp and pinch the breast, because grasping and pinching the breast is certainly nodular, which is normal breast tissue. It is important to note that “lumps that are grasped do not count, but only those that are pressed”. If you find any difference from the previous month through monthly breast self-examination and breast touching in the shower, you should promptly ask your doctor for a diagnosis.