Overview In order to facilitate clinical determination of treatment options, prognosis, and to make scientific and meaningful conclusions from the findings of breast cancer research, a uniform classification of breast cancer is essential. A unified classification of breast cancer is essential. However, the classification of breast cancer is still confusing, and there are several histological classification standards for breast cancer at home and abroad, which are not uniform in practical application. At the same time, because the histology of breast cancer is complex and there are many types of breast cancer, and often multiple types exist in the same cancer tissue or even in the same section, which adds to the confusion and difficulty of classification and increases the possibility of duplicate classification. The perfect classification of breast surgery Zhang Chenguang of Xinjiang Cancer Hospital requires concise, practical and repetitive classification, and can be considered in the context of its histological origin, pathomorphological features, clinical manifestations, biological behavior, different stages of tumor development and various aspects of prognosis. The established classification of breast cancer focuses on histogenesis, and also divides breast cancer into 3 categories from the combination of biological characteristics and morphology: non-invasive, early infiltrative or microfocal infiltrative and invasive carcinoma, and among invasive carcinoma, two categories of specific and non-specific types. From the intertwining of cancer cells and fibrous components, it can be further divided into medullary carcinoma, hard carcinoma and simple carcinoma. The basis of domestic breast cancer classification is the classification formulated at the National Breast Cancer Conference in 1961. 1983, through the study of 4,396 cases of breast cancer histology in China, a more reasonable histological classification of breast cancer was proposed, which divided breast cancer into four categories of non-invasive carcinoma, early invasive carcinoma, invasive special type carcinoma and invasive non-special type carcinoma, totaling 18 types. The difference between the 5-year and 10-year survival rates of the four types of breast cancer was highly significant (p<0.01). The salient feature of this classification, which is different from the previous classification, is that it reflects the different stages of development of breast cancer from non-invasive carcinoma (in situ) to early invasive to invasive carcinoma. In recent years, other new classification schemes for breast cancer have been proposed by domestic pathologists. For the classification of breast cancer, a perfect classification combining morphology and function is still expected. The classification of breast cancer (a) Principles of classification After observation of the primary cancer in pathological sections, a comprehensive judgment is made to classify it. Since breast cancer is mostly a mixed type of cancer, when several forms coexist, the diagnosis is named according to the dominant component, and the secondary components can be indicated afterwards. (2) Classification criteria 1. Non-invasive carcinoma (1) Intraductal carcinoma: The cancer cells are confined to the ducts. They do not break through the basement membrane of the duct wall. The cancer cells in the duct can be arranged into four characteristic images, namely ① substantial, ② pimple-like, ③ papillary and ④ sieve-like. These four images are often mixed, but one image is often predominant in a tumor. (2) Lobular carcinoma in situ: It occurs in the lobules and the cancer cells do not break through the terminal milk ducts or the basement membrane of the alveoli. The lobules are enlarged and the ductal vesicles are increased, obviously thickened and filled with non-polar cancer cells. The lumen of the ductal follicle and the myoepithelial cells disappeared. The cancer cells were slightly larger in size, consistent in shape and size, with richer and lighter stained cytoplasm. The nucleus is slightly larger, the chromatin is finer and more evenly distributed, and the nuclear fission phase is rare. 2. early infiltrative carcinoma (1) early infiltration of ductal carcinoma: cancer cells in ductal carcinoma break through the basement membrane of duct wall, start to produce buds and infiltrate into the interstitium. (2) Early infiltration of lobular carcinoma: Cancer cells of lobular carcinoma in situ break through the basement membrane of terminal milk ducts or alveoli and begin to infiltrate into the interstitial space of lobules, but still confined to the lobules. If it has reached outside the lobule, it is classified as invasive lobular carcinoma. 3. Infiltrative special type of carcinoma (1) papillary carcinoma: if the carcinoma parenchyma is mainly papillary structure with or without fibrous vascular bundle, it can be non-invasive or infiltrative papillary carcinoma. The infiltration often appears at the base of papillary hyperplasia. (2) Medullary carcinoma with massive lymphocytic infiltration: the carcinoma cells are large, with abundant cytoplasm, pale basophilic, indistinct cytosol, and often fused with each other. The nucleus is vacuolated, the nucleolus is obvious, and the splitting phase is common. The cancer cells are densely packed and often distributed in patches, occasionally with papillary structures or diffuse distribution. There is little interstitial fibrous tissue and the peri-cancerous boundary is clear. There is thick lymphocyte infiltration around the cancer nest. (3) Small ductal carcinoma (highly differentiated adenocarcinoma): the cancer cells are rectangular or columnar in shape, of fairly uniform size, with no obvious heterogeneity and few nuclear fission phases. Most of the cancer cells are arranged into single-layered glandular ducts of regular size and scattered to infiltrate the interstitium, causing fibrous tissue reaction. (4) Adenoid cystic carcinoma: Basal cell-like cells form lamellae or small nests of different sizes and shapes, with round luminae of varying numbers and uniform sizes inside. Myoepithelial cells can be seen on the luminal surface and around the cell lamellae. (5) Mucinous adenocarcinoma: The epithelial mucus component of the cancer parenchyma accounts for more than half of the total amount. Most of the mucus is outside the cells, forming a mucus lake; occasionally, it is inside the cells, appearing as printed ring-like cells. Sweat gland-like carcinoma: The carcinoma cells are large, rectangular, columnar or wedge-shaped, with abundant, eosinophilic granular cytoplasm, sometimes with parietal protrusions. The nucleus is mildly to moderately heterogeneous. The cancer cells form small nests, ducts or papillae, and the parenchyma and interstitium are often clearly separated. Other types of carcinoma with sweat-like changes should be excluded. (7) Flat cell carcinoma: The carcinoma parenchyma is all typical flat cell carcinoma, i.e. intercellular bridges and keratinization can be seen. If part of flat epithelial metaplasia occurs in other types of carcinoma, it is not included in this list. Papillary Paget disease: There are scattered or nested, cytoplasmically lightly stained cancer cells in the epidermis of the nipple or areola. The early cancer cells are mostly located in the basal layer and can later invade to the superficial layer. The skin of other parts of the breast is not infiltrated by cancer. This type coexists with ductal carcinoma or other invasive carcinoma. 4. Infiltrative non-specific carcinoma (1) Infiltrative lobular carcinoma: lobular carcinoma obviously infiltrates outside the lobules, including small cell type infiltrative carcinoma. The morphology of cancer cells resembles lobular carcinoma in situ. The cancer cells are often arranged in a single line, or in a target ring around the duct, or scattered in the interstitial fibers individually. Sometimes, residual lobular carcinoma in situ can be seen. (2) Infiltrative ductal carcinoma: The infiltrative component of ductal carcinoma does not exceed half of the carcinoma parenchyma. If the amount exceeds half, it is named according to the main form of its infiltrative component. (3) Sclerocarcinoma: The cancer cells are arranged in pieces or nests, dense, and may have adenoid structures. The interfibrous component is less than 1/3, and there is no large amount of lymphocytic infiltration. (4) Simple carcinoma: between hard carcinoma and medullary carcinoma, i.e. the ratio of carcinoma parenchyma to interstitial fibers is similar. The cancer cells mainly form irregular solid strips or small nests, and may also have adenoid structures. (5) Adenocarcinoma: The adenocarcinoma parenchyma has more than half of adenoid structures. Other rare carcinomas (1) Secretory carcinoma: the carcinoma cells are lightly stained, arranged into strips, glandular or nest-like, and have significant secretion phenomenon. There are amylase-resistant PAS-positive substances in the cancer cells and in the adenoid lumen. (2) Lipid-rich carcinoma (lipid-secreting carcinoma): the carcinoma cells are large, with transparent or foamy cytoplasm and strongly positive fat staining. The nucleus is irregular and the nucleoli are prominent. The arrangement of cancer cells is variable and may be accompanied by intraductal carcinoma or lobular carcinoma-in-situ components. (3) Adenofibroma carcinoma: some or all of the glandular epithelial cells in adenofibroma are malignant, which can be shown as intraductal carcinoma or lobular carcinoma in situ, and can further develop into invasive carcinoma. Other types of cancer invading adenofibroma should be excluded. (4) Papillomatous carcinoma: Focal cancerous tissue areas appear within the papillomatous lesions, and there are transitional changes in the morphology of both. The carcinoma area often appears as intraductal carcinoma. (5) Carcinoma with chemosis: In breast cancer tissues, various chemotactic changes are occasionally seen, such as the formation of flat cells in part of the adenoid epithelium; the appearance of bone and cartilage components in the interstitium. These tumors are still classified as the original tissue type, but the chemogenic grade should be indicated. (3) The general classification of breast cancer can be divided into the following 7 types according to the visual examination of breast cancer specimens. 1. Infiltrating type The tumor has unclear boundary and infiltrates into the surrounding tissues in the form of crab feet, and the cut surface is depressed, grayish white and hard. 2. The tumor has a clear border or pseudo-envelope, and grows towards the surrounding tissues with flat or slightly elevated surface, grayish yellow or grayish pink, soft texture, and sometimes necrosis. Cystic papillary tumor is cystic with clear border, in which there is papillary or lobulated tissue protruding into the cystic cavity, soft and brittle, and the cyst often contains dark brown liquid. It is soft and brittle, and often contains dark brown liquid. It is like intracapsular papillary carcinoma. .4. Acne-like lesions are more extensive, often without obvious boundary, granular in cut surface, and earthy yellow mud-like material can be seen in many places when squeezing the lesion area. The tumor has clear border, soft texture, smooth cut surface and translucent jelly-like. 6. Nipple eczema-like type: nipple erosion, oozing, crusting, or in severe cases, nipple and areola ulceration. 7. Multifocal type: 2 or more unrelated cancer foci exist in one breast at the same time, and their appearance can be any of the above types.