High-grade neuroendocrine carcinoma is usually categorized into carcinoid tumor and large or small cell carcinoma, and whether it is serious or not needs to be judged according to the type of high-grade neuroendocrine carcinoma. When the patient has carcinoid tumor, it is generally not considered to be serious, while if the patient has large or small cell carcinoma, it is relatively more serious. 1. Carcinoid tumor: Carcinoid tumor is an atypical type of high-grade neuroendocrine carcinoma, which usually has low recurrence and metastasis rate. If the patient is in good health, the prognosis is usually better after surgery, and the patient can basically be clinically cured after surgery, so carcinoid tumor is not considered to be a serious disease, but it should be paid great attention to and actively treated. 2. Large and small cell carcinoma: large and small cell carcinoma has a higher degree of malignant lesions and rapid development, which may spread and metastasize in a short time. After the onset of the disease, patients usually show symptoms such as loss of appetite, emaciation, abdominal pain and even upper gastrointestinal bleeding, etc. It is not easy to be stripped by surgery, and usually the prognosis is relatively poor. In addition, the severity of high-grade neuroendocrine carcinoma may also be related to the patient’s own physical condition, so it is recommended that the patient should consult a doctor for diagnosis in time, and the specific conditions should be based on the doctor’s advice.