In situ carcinoma of the breast is the earliest cancer among breast cancers, among which intraductal carcinoma is the most common and lobular carcinoma in situ is less common. In developed countries, due to the widespread use of mammography screening, the detection rate of in situ cancer has improved significantly compared with the previous diagnosis by conventional methods, and the basic research and clinical treatment of in situ cancer have also progressed rapidly. In contrast, there is a big gap between China and China, and the clinical diagnosis and treatment of in situ cancer is not standardized enough. I. Diagnosis of carcinoma in situ of breast: The growth and expansion of carcinoma are from carcinoma in situ to early infiltration to extensive infiltration. Breast cancer takes about 2-3 years from cellular carcinoma to tumor of 1cm, so there should be enough time for early detection and early diagnosis at the stage of carcinoma in situ, but unfortunately, more than 90% of those clinically diagnosed as breast cancer are invasive carcinoma, because there are no symptoms in the early stage of cancer and no lumps can be felt in the breast. In situ cancer with breast lumps as clinical manifestation is very rare. To improve the detection rate of carcinoma in situ, it should be detected from patients without symptoms and lumps. Large-scale screening and application of high-resolution mammography are the most effective measures and methods. In fact, there are some clinical signs related to carcinoma in situ, such as: recent local glandular thickening of the breast; nipple overflow showing continuous fixed single ductal blood or brown overflow (especially in postmenopausal women); nodular hyperplasia of the breast with recent local protrusion and hardening; recurrent eczema of the nipple, etc. If we can raise our vigilance, pay attention to these signs and follow them for further examination, it is believed that there will be more It is believed that more early cancers will be detected if we can be alert and follow these traces for further examination. Commonly used effective examination methods include: 1.Mammography. On high quality mammogram, carcinoma in situ is characterized by microscopic calcifications in the shape of lines or bifurcations. At present, high-resolution mammogram is equipped with 3D directional puncture biopsy device and digital system, which makes the examination more perfect. The positive rate of nipple discharge cytology examination is not high, but it is still routinely used. Biological markers of nipple discharge, such as CEA and c-erbB-2 determination, are of great value for the diagnosis of intraductal cancer with nipple discharge. In recent years, fiberoptic endoscopy has been used for the examination of patients with papillary overflow, which has added another valuable examination method for the detection and diagnosis of intraductal carcinoma. Any area suspected of cancer should be biopsied and, if necessary, serially sectioned for pathological examination. The morphological heterogeneity of breast cancer is also reflected in the diagnosis of carcinoma in situ. Third, it is not uncommon to diagnose and treat an invasive carcinoma as in situ carcinoma. This often occurs in the following two situations: 1. A frozen section during surgery is reported as intraductal carcinoma, but postoperative paraffin section is diagnosed as invasive ductal carcinoma. This often puts the surgeon in a dilemma in choosing the treatment: if treated as non-invasive carcinoma, simple mastectomy is sufficient for resection; however, in the face of invasive carcinoma after surgery, the surgeon has to take remedial measures such as second surgery for axillary lymph node biopsy or dissection, or axillary radiotherapy (blind radiotherapy without knowing the condition of axillary lymph nodes is not beneficial to patients who do not have metastasis, but has the disadvantage of increasing the complications of radiotherapy). (blind radiotherapy in the axillary lymph nodes without knowing the condition of the lymph nodes is not beneficial but may increase the complications of radiotherapy). In order to avoid the above situation, under the guidance of “prefer left to right”, as long as the diagnosis of breast cancer (whether it is in situ or invasive) is made, all patients are modified. Whether it is under-treatment or over-treatment, it will cause physical and mental trauma to patients. 2. Frozen section during surgery and postoperative paraffin pathology are diagnosed as carcinoma in situ, but after a certain period of time, axillary lymph nodes or other body transformation may also occur. The reason for the above situation is that for breast cancer with mainly in situ components and partial infiltration, due to the location of the section, or the small number of sections, or even only one or two sections, the diagnosis of in situ cancer is missed, resulting in a wrong diagnosis. Or in situ cancer with occult infiltrative foci (similar to occult breast cancer, where the primary lesion is not available and the first manifestation is lymph node metastasis in the axilla) is diagnosed as in situ cancer due to pathology (including intraoperative freezing and postoperative paraffin), so that breast conservation + radiotherapy or total mastectomy is performed according to the principle, and there is no basis for chemotherapy and targeted therapy after surgery for in situ cancer, so that local recurrence or distant metastasis may occur later. In fact, what is clinically important are those parts where cancerous tissue infiltration has occurred (? even if they are very small localized), rather than the in situ cancer components that are dominant in volume. 2.Treatment of breast carcinoma in situ: local surgical treatment is the main treatment for carcinoma in situ. Surgical methods: breast conservation plus radiotherapy; total mastectomy plus sentinel lymph node biopsy. Endocrine therapy for hormone receptor-positive patients. There is no basis for chemotherapy and targeted therapy for carcinoma in situ. For local recurrent carcinoma in situ after breast conservation, total mastectomy is the main treatment. If the recurrence is invasive carcinoma, it will be treated as invasive carcinoma.