 Multiple endocrine neoplasia type I (MEN1)can be found in carcinoid tumor patients, but not those with LCNEC and SCLC.Genetic changes are very high in SCLC and LCNEC, but usually low for TC, intermediate for AC.The diagnosis of SCLC, TC and AC can be made by light microscopy without the need for special tests in most cases, but for LCNEC it is required to demonstrate NE differentiation by immunohistochemistry or electron microscopy.