Neuroendocrine tumors (NETs) are mostly slow growing, but some are not and can possibly spread to other parts of the body They are classified by tumor grade which describes how quickly the cancer is likely to grow and spread.. 
Neuroendocrine tumors (NETs) are mostly slow growing. But some are not and can possibly spread to other parts of the body. They are classified by how quickly the cancer is likely to grow and spread (tumor grade) 