I. Concepts of breast cancer screening and early diagnosis At present, early breast cancer (EBC) usually refers to clinical stage I and II breast cancer according to TNM staging. Some experts also believe that true early breast cancer refers to histologically early cancer. Histologically early cancer refers to cancer that has not yet infiltrated into adjacent tissues and has not metastasized, i.e. non-invasive cancer, including ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS). However, these two conditions are pathologically classified as pre-cancerous lesions. Breast cancer screening is a cancer prevention measure for asymptomatic women to detect breast cancer early, to achieve early diagnosis and early treatment, and ultimately to reduce breast cancer mortality in the population. Early diagnosis of breast cancer is a diagnostic process to detect and diagnose non-invasive and non-salvageable breast cancer by using relevant screening and examination tools according to a certain screening and diagnostic process. With the development of breast cancer screening and early diagnosis, the increasing detection rate of non-invasive cancer has also improved the detection rate of clinical stage I/II EBC, especially the detection rate of T1a/b breast cancer, thus improving the survival rate and reducing the mortality rate of breast cancer. According to the SEER (Surveillance, Epidemiology, and End Results), since breast cancer screening and early diagnosis were introduced before 1975, the incidence of non-invasive cancer increased from 5.8 per 100,000 to 32.5 per 100,000 between 1975 and 2006, while the incidence of invasive cancer showed an increasing and then decreasing trend. Breast cancer mortality has continued to decline. This change in trend includes many factors, and screening and early diagnosis of breast cancer based on mammography (MG) is one of the important influencing factors. II. Methods of breast cancer screening and early diagnosis The results of clinical research trials on breast self-examination (BSE) have shown that BSE only improves the detection and biopsy rates of benign tumors, but does not improve the early diagnosis rate of breast cancer, nor does it effectively reduce the mortality rate of breast cancer. BSE is no longer recommended as a routine measure for the early diagnosis of breast cancer, but it is still recommended that women be informed of 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 an early diagnostic measure for breast cancer in asymptomatic women over 40 years of age. Breast imaging is a common method of breast cancer screening and diagnosis in China, and mammography (MG) is the standard method for breast cancer screening and early diagnosis. A large number of randomized clinical trials have confirmed that its use in breast cancer early screening can reduce breast cancer mortality. The advent of digital MG has further improved the accuracy of diagnosis. The sensitivity of MG in the diagnosis of breast cancer in fatty glands is 80%, but in dense glands, the sensitivity is only 30%. Breast ultrasonography (BUS) has the advantages of being easy to perform, non-invasive and economical. At present, domestic ultrasonography has become an important examination method in the early diagnosis of breast cancer and a complementary method to breast cancer screening (BI-RADS grade 2, 3, 0 women) or prior breast cancer screening, especially for women with dense glands. 9082 cases of Japanese breast cancer screening data reported by Uchida K et al. showed that breast ultrasonography could further detect 15% of breast cancers missed by MG. However, studies on the application of BUS breast cancer screening in China are underway, and some results are available. Magnetic resonance imaging (MRI) can be used as a complementary method for breast cancer screening and diagnosis, especially for MG and BUS-negative patients, because MRI has higher spatial and temporal resolution of soft tissues and is not affected by the denseness of the breast gland, so it can show breast lesions more clearly. In addition, MRI is more sensitive to multicentric and multifocal lesions. However, MRI is expensive and is generally recommended for screening only for women with a high risk of breast cancer such as those with a significant family history of breast cancer and breast cancer susceptibility gene (BRCA1/BRCA2) carriers. It is not currently used for screening in China. Breast ductoscopy (FDS) is a more commonly used method for early diagnosis of breast cancer in China, mainly for the etiological diagnosis of bloody nipple discharge. Our study suggests that 9% of bloody nipple discharge is caused by DCIS, while 52% of DCIS present with bloody nipple discharge, and more importantly, 50% of patients with DCIS whose main presentation is nipple discharge have no cancerous signs such as malignant calcified foci or masses detected by MG. It has an important role in the diagnosis, treatment and localization of intraductal lesions. About 80%-85% of breast cancers originate from the ductal epithelium, and ductoscopy has the advantage of direct visualization of ductal lesions and obtaining a large number of epithelial cells from the surface of the lesion, which is an important method for the diagnosis of DCIS. Pathology is still the gold standard for the diagnosis of breast cancer. FNA is simple, safe and economical, with a sensitivity of 65-98% and specificity of 34-100%; CNB can obtain enough tissue specimens for histopathological diagnosis and The sensitivity and specificity can reach 80-100%. 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, and the literature reports that the rate of missed lesions is only 1.1%, and for malignant lesions, the false-negative rate is only 1.0%. Currently, vacuum-assisted biopsy (VAB) technique has been widely used in clinical practice, especially for the diagnosis of inaccessible breast masses, and can detect 0.2-1% of early breast cancers in VAB of the breast considered benign disease. Compared with traditional surgical biopsy, VAB is less invasive, with less obvious postoperative scars and better cosmetic results. The cost-benefit ratio of health economics is also the most important indicator to measure the practical value of a public health measure. The current breast cancer screening in China still has a low detection rate compared with that in Europe and the United States, and there is no research data on screening to reduce breast cancer deaths. In China, where breast cancer screening resources are not abundant, establishing the high-risk groups for breast cancer in China and targeting screening is an important way to improve the cost-effectiveness of breast cancer screening. Some breast cancer susceptibility genes have been identified abroad, such as BRCA1, BRCA2, CYP17, CYP19, AT and other genes. However, at present, it is obviously impractical to conduct extensive susceptibility gene testing in China, and the breast cancer risk assessment systems established abroad, such as the FDA-approved Gail risk assessment model, are not necessarily suitable for the actual situation in China. Therefore, the establishment of a breast cancer risk assessment model suitable for women in China based on general epidemiological information is a topic worthy of further study. Qi Yali et al. collected domestic research literature on breast cancer risk factors from 1994 to 2006 for Meta-analysis, and the results showed that the top 5 breast cancer risk factors (OR) were benign breast disease (4.87), mental trauma (3.96), family history of tumor (3.68), time of menstruation (3.11) and breastfeeding time (2.95), in that order. Our study on the predictive model of breast cancer in women in Guangdong, using a case-control study, showed that among premenopausal women, taking birth control pills, having a relative with breast cancer, having bad mood, having adverse events, and being labor-intensive were risk factors for breast cancer; having a history of breast enlargement, having a history of breast tissue biopsy, and having relatively strenuous exercise may be protective factors for breast cancer. Among postmenopausal women, having a relative with breast cancer is a risk factor, and having strong emotional regulation is a protective factor; through multiple regression analysis, a logistic regression model for predicting breast cancer in pre- and postmenopausal women was established, and the correct rate of the premenopausal model for predicting no breast cancer was 74.2%, and the correct rate of breast cancer occurrence was 57.8%. The postmenopausal model was 80.5% correct in predicting the occurrence of breast cancer and 64.4% correct in predicting the non-occurrence of breast cancer. However, a few studies in China have not been able to come up with a mathematical model of breast cancer risk, and clinical application has to wait. In addition, how to standardize the process of breast cancer screening and early diagnosis in China, such as the determination of the screening population, the selection of technical means and mode of screening, the frequency and time interval of screening, the training and qualification of screening and diagnostic personnel, how to ensure the quality of screening, etc.? It is still a major problem and challenge for us to find out the breast cancer screening and early diagnosis model that meets our national conditions. In future studies, we should focus on the issue of imaging assessment standards in breast cancer screening and early diagnosis, and promote the BI-RADS grading system for imaging, especially ultrasound, to increase the comparability of study results. It is necessary to promote the BI-RADS grading system to unify the standards of supplemental examinations and biopsies, to increase the rate of supplemental examinations and biopsies, to avoid excessive false positive rate, to reduce unnecessary pathological biopsies, and to increase the positive biopsy rate in order to further the level of breast cancer screening and early diagnosis in China. The level of screening equipment and professional diagnostic personnel varies greatly among medical units of different levels in different regions, and the investment in equipment and personnel training in primary hospitals and maternal and child health institutions should be strengthened to improve the technical level and reduce the rate of missed diagnosis. At present, most of the research reports on breast cancer screening in China are the results of a single screening of a certain population, and there is a lack of information on long-term planned screening studies. It is necessary to strengthen the cost-benefit analysis of health economics, so that breast cancer screening can become a long-term public health project and improve women’s health.