High-grade neuroendocrine carcinoma refers to less differentiated tumors that have the ability to secrete endocrine hormones and are derived from neuroendocrine cells, and are commonly found in the gastrointestinal tract and other digestive systems. Neuroendocrine tumors are mainly derived from neuroendocrine cells and are classified into high-grade and low-grade tumors according to the degree of differentiation of the tumor. High-grade neuroendocrine tumors have a lower degree of cell differentiation and relatively higher degree of malignancy, and are also known as high-grade neuroendocrine carcinomas. They include small cell neuroendocrine carcinoma, large cell neuroendocrine carcinoma and other types. High-grade neuroendocrine carcinoma may be located in gastrointestinal tissues, lungs, thymus, uterine cervix, etc. Depending on its location, compression symptoms such as dysphagia and obstruction, neuroendocrine symptoms such as Zuoai syndrome and Cushing syndrome may appear. It is recommended to go to the hospital in time for consultation if the above symptoms appear or if high-grade neuroendocrine cancer is suspected.