Carcinoid tumor is a solid tumor that originates from silver-loving cells at the base of the intestinal canal, mostly located in the gastrointestinal tract and respiratory tract, and its histological characteristics are a slow-growing tumor with very low malignancy. It is a series of syndromes such as skin flushing, diarrhea, asthma and heart valve disease, which are clinically known as carcinoid syndrome. Carcinoid tumors can occur not only in the gastrointestinal tract and bronchi, but also in the pancreas and bile ducts. From this perspective, carcinoid tumor and cancer are still essentially cancer, but the least malignant type of cancer.