Table 1.

Features of EECs of colon and rectum

Cell type	Distribution	Ultrastructural features	Secretory granules	IHC	Secretory products
EC cell	Most common EEC type; throughout GIT	Pyramid shaped; often have slender apical process reaching luminal surface	150–500 nm; pleomorphic	CgA, Syn, 5-HT, TPH	5-HT
D cell	Throughout GIT. Least common EEC type in colon and rectum	Spindle shaped; often have slender apical process and one shorter wider basal extension	150–300 nm; round	(Syn), somatostatin	Somatostatin
L cell	Found in duodenum to rectum; rare before terminal ileum; greatest frequency in rectum	Bottle shaped; often have apical process reaching luminal surface; sometimes have basal process along basement membrane	200–400 nm; round	(CgA), (Syn), PYY, GLP-1, GLP-2, oxyntomodulin, glicentin	Peptide YY, GLP-1, GLP-2, glicentin, oxyntomodulin

IHC, immunohistochemistry; EEC, enteroendocrine cell; GIT, gastrointestinal tract; CgA, chromogranin A; Syn, synaptophysin; 5-HT, serotonin; TPH, tryptophan 5-hydroxylase; PYY, peptide YY; GLP-1, glucagon-like peptide 1; GLP-2, glucagon-like peptide 2.