Recently I received a 65-year-old febrile patient in the outpatient clinic who was diagnosed with non-Hodgkin’s lymphoma – diffuse large B-cell type a few months ago. After applying R-CHOP regimen chemotherapy for a few cycles, he developed fever and his body temperature fluctuated between 39~40℃, and the doctor gave the application of many kinds of antibacterial and anti-inflammatory drugs, but the effect was not good, and the fever persisted for more than a month. The patient was very distressed and anxious and asked, “Director Zhang, what is wrong with my fever? Can I still control this fever?” In fact, tumor patients often encounter these problems. Doctors will also encounter such problems in the process of diagnosing and treating tumors. Fever may seem to be a simple condition, but for tumor patients, the diagnosis and treatment are quite tricky and difficult. Some oncology patients, in the case of lymphoma patients for example, will present with fever, night sweats and weight loss, which are called B symptoms. About 10% of patients can develop systemic symptoms such as fever, itchy skin, night sweats and weight loss, which can also be the earliest clinical manifestations. Among them, fever is the most common. About 30-40% of patients with Hodgkin’s lymphoma have persistent fever of unknown origin as the starting symptom. These patients are usually older, predominantly male, and often have retroperitoneal lymph node involvement. Periodic fever is seen in about 1/6 of patients. Some patients have prolonged irregular fever of unknown origin, and superficial lymph nodes are eventually found to be enlarged after 2 years, and the diagnosis is made clear only after biopsy. There are also a few patients who do not have enlarged superficial lymph nodes but have prolonged fever, first periodic and later becoming persistent, with multiple examinations failing to determine the cause, and finally CT examination and puncture confirming retroperitoneal lymphoma. Tumor patients often have immune dysfunction and immunocompromise. Chemotherapy drugs can suppress the immune function, thus the immune deficiency is more prominent in patients after chemotherapy. Patients are often prone to co-infection, especially after multiple cycles of chemotherapy, the patient’s constitution decreases and immunity is extremely low, which makes it very easy to combine bacterial, viral or fungal infections. The original fever of tumor patients is controlled by chemotherapy and the fever subsides, and tumor fever can appear again after the disease progresses. Therefore, after several cycles of chemotherapy for tumor patients, the patient develops fever, is this fever caused by infection? Or is this fever caused by the disease progression of the tumor itself? This has confused many doctors and patients. Sometimes the doctor applied antibiotics, antiviral drugs or antifungal drugs to the patient, but the patient still had fever, and then the doctor changed another round of antibiotics, antiviral drugs or antifungal drugs to the patient, but the patient still had fever. After the doctor has changed the patient for round after round of antibiotics, antivirals, or antifungals, the patient’s temperature is still not well controlled. If it is infectious fever and the infection is not controlled in time, then the tumor disease that has been controlled will revive and the disease will progress beyond the next cycle of chemotherapy; or if the infectious fever is treated with chemotherapy according to tumor fever, it will further weaken the patient’s immune function and constitution, and the infection will become more and more difficult to control. If the fever is tumorigenic and anti-infection treatment is given all the time, the tumor condition will further develop. At this time, doctors are helpless, patients and family members are anxious, and the treatment process seems to be in a deadlock. So, is it true that persistent fever in tumor patients is unrecognizable and uncontrollable? However, there are some distinguishing points between fever caused by tumor and fever caused by infection. 1. Fever type. The fever caused by tumor disease is mostly of regressive fever or flaccid fever type, sometimes the body temperature fluctuates greatly within a day, and sometimes the body temperature can drop to normal range by itself. In contrast, infectious fever has a rapid onset and the body temperature can rise to a high level within a short period of time, and rarely decreases to normal without antipyretic treatment. 2. Evidence of fever. Infectious fever can mostly find foci of infection or pathogens, while pathogenic examination of fever caused by tumor is mostly negative, and evidence of tumor progression can often be found; 3. Hormone sensitivity. Infectious fever is ineffective or transient to hormone therapy (duration about 2-6 hours), while lymphoma fever is often effective to hormone therapy (duration about 24-48 hours). 4, the impact on general condition Infectious fever patients often have poor mental diet, can appear systemic toxic symptoms, and their physical condition often decreases after a period of fever; while tumor fever has less impact on patients’ general condition; 5. , blood picture performance. Infectious fever has elevated leukocytes and neutrophils, while tumor fever has normal leukocytes except for special types of lymphoma; 6, signs before fever Infectious fever has chills before fever, while tumor fever patients often do not realize that their body temperature has increased; 7, the effect of anti-pathogenic treatment tumor-induced fever is ineffective with anti-pathogenic drug therapy and effective with chemotherapy; while infectious fever can be treated with sensitive anti-pathogenic drugs. The fever can be controlled after the treatment of anti-pathogenic drugs. In fact, there is another clinical fever type, which is the fever caused by the disturbance of internal environment (including endocrine function disorder, electrolyte disorder, abnormal liver and kidney function, immune function disorder, etc.), that is, the fever caused by the imbalance of yin and yang in Chinese medicine. These patients have no evidence of either tumor disease progression or pathogenic infection. The fever is mostly around 38°C. There is no chill before the fever, and the body temperature will automatically drop to normal after the patient drinks some boiled water or sweats. The fever has no significant effect on the patient’s physical condition. For this type of fever, the treatment should be to adjust the internal environment, replenish or correct the internal environment dysfunction or biochemical indexes, and apply some immunomodulatory drugs as appropriate. In conclusion, the above three fever types should be treated separately. Clinically, some patients may have a mixture of two or three fever types, and these patients should be treated in a holistic manner. Some infectious fever patients whose fever is still not controlled after applying multiple powerful anti-pathogenic drugs should promptly do corresponding chest and abdominal examinations, and must exclude whether it is tumor disease progression. There are also some febrile tumor patients who are considered to have tumor disease progression after CT, MRI or ultrasound examination (e.g., new lesions or enlargement of existing lesions are found in the hilum, mediastinum or retroperitoneum), and after repeatedly changing chemotherapy regimens for chemotherapy with poor results, finally another biopsy or puncture is proved to be combined with pulmonary tuberculosis or squamous lung cancer, adenocarcinoma of digestive tract or soft tissue sarcoma. Therefore, fever that is difficult to control or repeated chemotherapy is ineffective should be re-examined by CT, MRI or ultrasound or/and re-pathological biopsy of the mass to clarify the diagnosis and avoid mistreatment.