In today’s society, the incidence of breast cancer is getting higher and higher, but some people can survive long-term for 10 or 20 years after treatment, while others recur, metastasize and die in 2 or 3 years, why? According to the current research results, scientists use gene expression profiling technology to classify breast cancer into 5 molecular subtypes, namely ① luminal A, ② luminal B, ③ HER2 overexpression, ④ basal-like, and ⑤ normal breast-like. Of these, the last category is thought to arise from possible tissue contamination. It has been found that aspects such as patient prognosis and treatment response are significantly related to the first four classifications mentioned above; in other words, different molecular types of breast cancer have different degrees of malignancy. In other words, although they are all bad guys, they are also divided into big bad guys and small punks who can be rehabilitated for good. But gene expression profiling tests are, after all, expensive and not very easy to popularize. People then tried to find an easy method that could be an alternative. After years of practice, scientists found that some data obtained using immunohistochemistry could be an approximate substitute for complex genetic testing techniques for molecular typing of breast cancer. The data obtained by immunohistochemistry are in the patient’s pathology report, and the molecular typing of breast cancer can be performed simply by using a combination of four common antibodies. They include estrogen receptor (ER), progesterone receptor (PR), HER2 and Ki-67 (cell proliferation index). Different types of breast cancer can be harmful to patients in different ways. Statistically, “dagger-wielding punks” account for about 45-70% of all malignants, so the majority of breast cancer patients have a good prognosis. The prognosis is also good for “gun-toting killers”, which account for about 8% of all cases. The “mob with assault rifles” is about 15% and can be well relieved by chemotherapy and targeted therapy. The worst prognosis is the “bazooka-carrying” triple-negative breast cancer, which accounts for 10-15% of all malignant patients. Although this type of breast cancer is sensitive to chemotherapy, it is prone to recurrence and metastasis, which is the most harmful to patients. However, treatment cannot be done mechanically based on the above molecular typing alone, for example, patients with Luminal A type can be treated with endocrine therapy alone. However, if the lesion is long-lasting and metastasis occurs in the axillary lymph nodes or even other sites, then it is not only endocrine therapy, but also chemotherapy or even radiotherapy. It’s like saying that if the dagger-wielding punks are not eliminated for a long time and grow up to be an axe gang, the danger is also huge! After all, modern technology is developing rapidly and new treatment methods are coming out all the time, so the types of diseases that we could not do anything about before can be easily dealt with now!