The breast is an organ located on the surface of the body, so it is easier to perform physical examination when lesions occur; however, the breast is an important endocrine organ of women, and it can have different changes at different times of life and during the menstrual cycle, which may sometimes conceal the existence of malignant tumors, while sometimes normal changes may be mistaken for tumors. For example, the following are easily confused: lobular hyperplasia and early breast cancer; acute mastitis and inflammatory breast cancer; glandular hypertrophy during pregnancy and lactation and breast cancer during pregnancy and lactation; plasma cell mastitis and mid- to late-stage breast cancer; inflammatory nipple erosion and breast Paget’s disease; breast surgery scar and breast cancer recurrence; male breast hypertrophy and male breast cancer; sebaceous cysts and lipomas and breast lumps; breast fibroadenoma and early lobulated cystic sarcoma, etc. Therefore, a careful and proper breast examination can help detect breast tumors and identify benign and malignant changes in the breast. When there is a lump in the breast, a physical examination by an experienced breast specialist may have a higher diagnostic accuracy than auxiliary examinations such as mammograms. Early detection, early diagnosis and early treatment have now become important strategies to control breast cancer. However, the clinical manifestations of early breast cancer are mostly atypical, therefore, a new concept of “early breast cancer” should be established, that is, “lump” should not be considered as the primary sign essential to diagnose breast cancer. In China, 77 cases of early breast cancer without lumps were reported, mainly due to the importance of clinical manifestations such as glandular thickening, nipple discharge and nipple erosion, which were found after further examination. In addition, such as mild nipple retraction, mild indentation of the breast skin, mild edema of the areola and the presence of breast pain after menopause are all valuable clinical manifestations. Because mammography can detect breast cancer that is negative on clinical examination, it is considered an important tool for early detection, but it is important to note that about one-third of early breast cancers cannot be detected by x-ray and are detected by clinical examination alone. In order to detect and treat breast cancer in time, and to exclude the psychological burden caused by some benign breast lesions, it is recommended that women should seek medical attention and undergo breast physical examination as soon as they find abnormalities in their breasts, such as pain, lumps, nipple overflow, etc. For women with high risk factors for breast cancer, such as immediate family members with breast cancer and previous history of breast cancer, it is recommended to have regular breast examination for early detection and treatment. Visual examination is mainly to observe the development of breast, whether the breast is symmetrical, similar in size, whether the nipples are in the same position, whether there is erosion, retraction or overflow of nipple, and whether there is any abnormality of breast skin. Palpation of the breast is very important. Especially when examining the lump, the doctor will pay attention to the location, size, boundary, texture, mobility, adhesions to the skin and pectoral muscles, etc., so as to make a judgment on the nature of the lesion. During palpation, experienced physicians will often gently lift the breast with their hands or increase the skin tension to find out if the skin is depressed after slight pulling, if so, it often indicates the possibility of early breast cancer. To examine the relationship between the mass and the deeper tissues, the patient is sometimes asked to cross both arms so that the pectoralis muscle is in contraction, or if the mass invades the pectoralis fascia or pectoralis muscle then the affected breast is elevated and movement is limited during the contraction of the pectoralis muscle. The breast surface should be palpated with two flat fingers in the quadrant or clockwise direction, and the breast should not be grasped and pinched with the fingers to avoid mistaking the normal breast tissue for a lump. 2. Axillary and supraclavicular lymph nodes are the regional lymph nodes of breast cancer, so palpation of the axilla is also part of the physical examination. Sometimes occult breast cancer is detected by palpating lymph nodes in the axilla. The examination is usually performed in a sitting position, with the patient’s arm held up by the examiner so that the armpit is naturally relaxed to facilitate the examination. The supraclavicular lymph node examination is usually performed by touching the patient’s supraclavicular fossa with both thumbs. In addition to clinical breast examinations, women of all ages can learn to do self-examinations of the breast. This is a simple and cost-effective means of early detection of breast cancer, but requires some training. Breast self-examination is usually performed once a month, and the examination time for premenopausal women should be the 9th to 11th day after menstruation, when endocrine hormones, mainly estrogen, have the least effect on the breast and the breast is in a period of relative quiescence and abnormal breast changes are most easily detected. If a lump is found during breastfeeding, it should be examined again after stopping breastfeeding.