Most common site for carcinoid tumor is
Carcinoid tumour arise from the enterochromaffin cells (Kulchitsky cells) found in the crypts of Lieberkuhn. These cells are capable of APUD (Amine precursor uptake and Decarboxylation) and can secrete vasoactive amines like 5- HT, 5-HIAA, 5-HTP; tachykinins, peptides (chromogranins)and PGs. It commonly occurs in appendix (45%), ileum (25%) and rectum (15%). Other (15%) sites are--other pas of GIT (including pancreas and biliary tract), bronchus and testis. Reference: page 877 SRB's manual of surgery 5th edition.
Esophagus
Lung
Appendix
Ileum
Urology