What test indicators are abnormal to indicate neuroendocrine tumors? Functional neuroendocrine tumors are associated with hormone overproduction, so abnormal elevation of certain hormone levels detected in the serum is highly suspicious of neuroendocrine tumors. In particular, a tumor marker called chromogranin A (CgA) is the most valuable universal marker for neuroendocrine tumors. Elevated serum CgA levels can not only indicate neuroendocrine tumors, but also assess the patient’s response to treatment and prognosis. If neuroendocrine tumor is suspected, how to confirm the diagnosis step by step? For patients with suspected neuroendocrine tumors, the physician will first perform a variety of tests to help determine the location of the tumor and also test the patient’s serum CgA. Then, the physician will perform a pathological examination of the lesion to help make a definitive clinical diagnosis. After these tests, the doctor will be able to determine not only if the patient has a neuroendocrine tumor, but also further determine which type of neuroendocrine tumor it is, and grade and stage the tumor. How to choose to use colonoscopy, CT, MRI and other examinations in diagnosis? Despite the rapid development of laboratory tests and imaging techniques, the diagnosis of neuroendocrine tumors is still delayed by about 5-7 years on average. Therefore, in order to improve the detection rate of primary tumors, it is recommended to take multiple imaging examinations if necessary, and perform CT, magnetic resonance imaging (MRI) and growth inhibitor receptor imaging (SRS, which labels radionuclides on tumor tissues for localized diagnosis of tumor foci and metastases) simultaneously for localization.