1. Breast self-examination and clinical breast examination Breast self-examination (BSE) is performed regularly by women on their own to improve the early detection of breast cancer, but the sensitivity of BSE is only 20-30%. The results of current clinical research trials show that BSE only improves the detection and biopsy rates of benign tumors, but does not improve the early diagnosis of breast cancer, nor is it effective in reducing breast cancer mortality. Therefore, the American Cancer Society guidelines no longer recommend BSE as a routine measure for early diagnosis of breast cancer, but still recommend informing women about the possible potential benefits (increased self-awareness) and limitations (mainly false-positive rates) of BSE. Clinical breast examination (CBE) is an examination performed by a physician trained to palpate the breast in asymptomatic women and has a sensitivity of 58.8% and specificity of 93.4%. There is still a lack of clinical trials evaluating the use of CBE alone for the early diagnosis of breast cancer. The American Cancer Society guidelines still recommend CBE as a measure for early diagnosis of breast cancer in asymptomatic women over 40 years of age. Mammography (MG) is the most common method for early diagnosis of breast cancer, and a large number of randomized clinical trials have confirmed that its use in early screening of breast cancer can reduce the mortality rate of breast cancer. The advent of digital MG can further improve the accuracy of diagnosis. The sensitivity of MG in the diagnosis of breast cancer in adipose glands was as high as 80%, but in patients with dense glands, the sensitivity was only 30%. Breast ultrasonography (BUS) has the advantages of being easy to perform, noninvasive, and economical. With the application of high-frequency ultrasound probes, the resolution of ultrasound has been further improved. Currently, BUS has become an important screening method in the early diagnosis of breast cancer, especially for women with dense glands, and an important complementary screening tool for MG. 9082 cases of Japanese breast cancer screening data reported by Uchida et al. showed that BUS examination could further detect 15% of breast cancers missed by MG. Traditional ultrasound probes with handheld probes lack uniform operating standards, store little information, and are easily influenced by subjective factors, thus limiting their application. In recent years, automated whole breast ultrasound (AWBU) has emerged to effectively address these problems, with the help of a computer system that can store information about the entire breast image and help analyze the lesion for diagnosis. The literature reports that AWBU can further improve the detection rate of breast cancers smaller than 25px. In addition, based on the principle that the elasticity (or hardness) of the tissue is closely related to the nature of the lesion, the advent of elastography and palpation imaging techniques of ultrasound has enriched the diagnostic breast ultrasound technology, but its wide application in clinical practice still requires further research. Magnetic resonance imaging (MRI) has a higher spatial and temporal resolution of soft tissues and is not affected by the denseness of the breast gland, which shows breast lesions more clearly. In addition, MRI is more sensitive to multicentric and multifocal lesions. However, MRI is expensive and is generally recommended only for screening of women with a significant family history of breast cancer and breast cancer susceptibility gene (BRCA1/BRCA2) carriers, as an adjunct to mammography and ultrasonography. 3.Breast ductal endoscopy The diagnosis of bloody nipple discharge is an important issue in the early diagnosis of breast cancer in China. The data of our hospital shows that 9% of bloody nipple overflow is caused by DCIS, while 52% of DCIS present as bloody nipple overflow, and more importantly, 50% of DCIS patients with blood overflow from nipples as the main manifestation have no cancerous signs such as malignant calcified foci or masses detected in MG. Breast ductal endoscopy (FDS) is a miniature endoscope that can directly observe breast ductal lesions and perform intraductal biopsy and cytological examination, which are important in the diagnosis, treatment and localization of intraductal lesions. About 80%-85% of breast cancers originate from ductal epithelium, and ductoscopy has the advantages of direct observation of ductal lesions and obtaining a large number of epithelial cells from the surface of the lesions, so it is possible to detect breast cancer years earlier than imaging. Pathological diagnosis is still the gold standard for breast cancer diagnosis. Currently, the pathological diagnosis of breast cancer includes fine needle aspiration cytology (FNA), hollow-core needle aspiration biopsy (CNB), vacuum-assisted biopsy (VAB) and traditional surgical biopsy; FNA has the advantages of simplicity, safety and economy, but cannot provide histological diagnosis, while most scholars believe that in cases where clinical manifestations, imaging and FNA are suggestive of malignancy, despite the lack of histological CNB can obtain sufficient tissue specimens for histopathologic diagnosis. For non-palpable breast lesions, imaging-mediated puncture biopsy or localized open surgical biopsy is the gold standard for definitive pathologic diagnosis of these subclinical breast lesions, with a 1.1% missed lesion rate and a 1.0% false-negative rate for malignant lesions as reported in the literature. Currently, the VAB technique has been widely used in clinical practice and has a higher biopsy success rate and accuracy compared to general puncture biopsy, which is close to traditional open surgical biopsy, while it is less invasive, has less obvious postoperative scars, and has good cosmetic results compared to traditional surgical biopsy.