Breast cancer patients with fever may have the following conditions: 1) Tumor fever, due to the high number of tumor cells in the late stage of malignant tumor, many pyrogenic cells are released, resulting in fever, which indicates a poor prognosis. 2) Infection, especially lung infection, breast cancer patients have a weak constitution and poor resistance, so it is easy to have infection, especially when lung infection occurs in breast cancer. Brain metastasis, though rare, can easily occur in the late stage of breast cancer. This kind of fever is characterized by high fever, exceeding 39℃, without infection or poisoning, and the effect of general antipyretic drugs is not good.