Neuroendocrine carcinoma is a type of cancer with endocrine function and is often classified as large cell neuroendocrine carcinoma, carcinoid tumor, atypical carcinoid tumor, and small cell carcinoma. Carcinoid tumors are the best treated and can generally be removed with low metastasis and recurrence rates. Small cell carcinoma is highly malignant and progresses rapidly. Atypical carcinoid tumor is equivalent to what people often call cancer. Large cell carcinoma is also highly malignant. Gastrointestinal neuroendocrine carcinoma includes two types of carcinoid tumors and small cell neuroendocrine carcinoma, which often appear as submucosal tumors and without envelope, and the treatment of gastrointestinal neuroendocrine carcinoma is mainly surgery.