Pain around umbilicus of lung cancer patients may be caused by metastasis of cancer cells, or spontaneous peritonitis, side effects of chemotherapy, etc. 1. Cancer cell metastasis: patients with lung cancer may have systemic metastasis in the late stage, and when metastasis reaches the abdominal cavity, it will cause digestive symptoms such as pain around the umbilicus, diarrhea and so on. 2. Spontaneous peritonitis: due to peritoneal metastasis or hypoproteinemia, patients with lung cancer may have fluid accumulation in the abdominal cavity. When the fluid accumulation is relatively large, spontaneous peritonitis may occur and cause pain around the umbilicus, which is usually accompanied by fever, vomiting and other symptoms. 3. Side effects of chemotherapy: generally, patients with middle and late stage lung cancer need chemotherapy, and commonly used chemotherapeutic drugs are cisplatin, carboplatin, etc. The common side effects of these chemotherapeutic drugs are abdominal pain, nausea, vomiting and other gastrointestinal symptoms. In addition to the above factors, other causes can not be ruled out. It is recommended to consult the doctor in time, carry out the corresponding examination for clarification and active treatment.