In 1907, Dr. Oberndorfer discovered a low-invasive epithelioid tumor that was considered to be a benign tumor similar to carcinoma and named it carcinoid tumor. By 1929, he found that not all carcinoid tumors are inert, some of them develop rapidly and can metastasize, and the name “carcinoid tumor” has been widely used among clinicians. 1980, the World Health Organization (WHO) first classified gastroenteropancreatic neuroendocrine tumors according to their histopathological features, and updated it in 2010. Therefore, carcinoid tumor is currently named as neuroendocrine tumor. Is carcinoid tumor a cancer? Let’s first talk about what is the difference between cancer and tumor? Then let’s clarify what is cancer? The terms cancer and tumor are often used in common, and generally there is not much problem. There are some differences between these two terms if we have to get into it. The key word of tumor is “solid”, and the property of cancer is “malignant”, so malignant solid tumor is cancer, blood cancer is not tumor, and benign tumor is not cancer. In mathematical formula, tumor = benign tumor + malignant tumor Cancer = malignant tumor + blood cancer Carcinoid tumor is also called neuroendocrine tumor, so is neuroendocrine tumor cancer? Director Xie explained it like this: whether carcinoid tumor is cancer depends on the differentiation degree of tumor tissue. If the differentiation is good and its biological behavior is benign, then it cannot be called cancer; if it is malignant, then it is cancer. In other words, not all carcinoid tumors are cancerous, and it ultimately depends on the result of pathology report.