Breast cancer is considered a major disease because it is one of the malignant tumors that may metastasize, recur, spread, and so on. In terms of treatment, it requires surgery, chemotherapy, targeted therapy, immunotherapy, endocrine therapy, etc. Therefore, it takes a lot of time and experience for the patient, and of course, the cost of treatment. If a patient has breast cancer, he or she needs to undergo regular treatment, including surgery or other treatments after surgery, and so on. After the treatment is completed, it is also necessary to go to the hospital for regular review to prevent the tumor from metastasizing or spreading. It is also worth mentioning that although ductal carcinoma in situ or lobular carcinoma in situ is also breast cancer, most insurance companies currently do not classify these two types of breast cancer as major diseases.