There are four types of breast cancer: non-invasive, invasive specialized, invasive non-specialized and other rare types. There is no such thing as “the most serious” breast cancer, but invasive specialized carcinoma and invasive non-specific carcinoma are the more serious types of breast cancer, because the cancer cells can infiltrate and metastasize. 1. non-invasive carcinoma: refers to the lesion is limited to the primary site without metastasis, and can be categorized into ductal carcinoma in situ, lobular carcinoma in situ, and nipple eczema-like breast cancer. 2. invasive special carcinoma and invasive non-specific carcinoma: it means that the cancer cells have infiltrated and extensively invaded the surrounding tissues, which may easily cause metastasis of the cancer foci. Invasive specialized carcinoma includes papillary carcinoma, sweat adenocarcinoma, adenoid cystic adenocarcinoma and mucinous adenocarcinoma, etc. Invasive non-specific carcinoma includes invasive ductal carcinoma, invasive lobular carcinoma and simple carcinoma. 3. Other rare carcinomas: the histopathological classification is mostly based on the microscopic features of the tumor rather than its biological behavior, such as spindle cell carcinoma and indolent cell carcinoma. Breast cancer refers to the phenomenon of uncontrolled proliferation of breast epithelial cells under the action of various carcinogenic factors. Symptoms such as breast lumps, nipple discharge and enlarged axillary lymph nodes may occur in early stage. It is recommended that patients with the above symptoms should go to the hospital in time. If diagnosed, the specific type of breast cancer should be clarified and symptomatic treatment should be carried out under the guidance of doctors.