Neuroendocrine carcinoma of the gastrointestinal tract is a type of cancer with endocrine function. It is often divided into large cell neuroendocrine carcinoma, carcinoid tumor, atypical carcinoid tumor, and small cell carcinoma. Carcinoid tumor is the best, usually resection is sufficient, metastasis and recurrence rate are low. Small cell carcinoma is highly malignant and progresses rapidly. Atypical carcinoid tumor is equivalent to what we often call cancer. Large cell carcinoma is also highly malignant. Classification: Gastrointestinal neuroendocrine carcinoma includes carcinoid tumor and small cell neuroendocrine carcinoma. Microscopic features: It often appears as a submucosal tumor with mucosal elevation or ulcer formation on the surface and grayish-yellow color without envelope on the cut surface. The tumor cells are composed of small to medium-sized cells with indistinct cytoplasmic boundaries, round and regular nuclei, arranged in sheets, cords, clusters, glandular or chrysanthemum-like clusters. In poorly differentiated cases, the cancer cells are smaller, with less cytoplasm, and the nuclei are often angular and deeply stained, with splitting images. Neuroendocrine granules with a diameter of 200-300 nm can be seen under electron microscopy. Diagnosis: Endoscopic and pathological examination, 24h urine 5-HIAA (metabolite of 5-hydroxytryptamine) are helpful for diagnosis; immunohistochemical assay has special diagnostic value, and the neuroendocrine markers NSE, CHG2A and synaptic vesicle protein (Sy) are generally used for identification. Differential diagnosis: Neuroendocrine carcinoma of gastrointestinal tract should be differentiated from hypofractionated adenocarcinoma. positive immunohistochemistry for NSE and CHG2A can confirm neuroendocrine tumor. negative CEA and negative Gas can exclude hypofractionated adenocarcinoma and gastrinoma, respectively. Combined with the gross, histomorphological and its clinical highly malignant biological behaviors, the diagnosis of gastric neuroendocrine carcinoma can be made. Treatment: The treatment of gastrointestinal neuroendocrine carcinoma is based on surgery. The scope of surgery depends on the size, location, degree of infiltration, lymph node involvement and whether liver metastasis is present in the primary tumor. The scope of surgery depends on the size, location, degree of infiltration, lymph node involvement and whether liver metastases are present. According to the biological characteristics of gastrointestinal neuroendocrine carcinoma, it is generally believed that the principles of surgical treatment are as follows: local resection can be performed for carcinoma of the stomach, appendix and rectum with tumor diameter less than 2 cm, not infiltrating the muscular layer and without lymph node metastasis; radical surgery is required for carcinoma of the small intestine and colon or carcinoma larger than 2 cm, infiltrating the muscular layer and with lymph node metastasis; for metastatic carcinoma, if the general condition allows, palliative primary surgery is feasible. For metastatic carcinoid tumors, palliative resection of primary foci and metastases is feasible if the systemic condition allows. Based on the above principles, different surgical methods are used for gastrointestinal carcinoid tract. For multifocal and mixed carcinoid tumors and small cell neuroendocrine carcinoma, the scope of resection should be expanded appropriately, and the surgical approach is the same as that for GI adenocarcinoma. Prognosis: The prognosis of gastrointestinal tract carcinoid tumor is generally better than that of adenocarcinoma. The prognosis is similar to that of benign tumor if the diameter is less than 2 cm, but worse if the diameter is greater than 2 cm or there is lymph node metastasis; the prognosis of multifocal or mixed carcinoid tumor and small cell neuroendocrine carcinoma is even worse. The postoperative follow-up of this disease should be paid attention to, in which the liver ultrasound and CT should be reviewed regularly for cases with higher malignancy, and the concentration of biogenic amines and peptide metabolites in urine (52HIAA, etc.) should be dynamically detected, and chemotherapy, biologic therapy and other comprehensive treatment measures should be selectively supplemented to improve the survival rate.