Carcinoid tumor in a Meckel's diverticulum: hypothesis on mutual embryological origin.

Congenital defects presenting at an adult age are subject to diagnostic errors because of their relative rarity and often odd clinical presentation. We illustrate a 63-year-old male patient with multiple ileal carcinoid tumors along with a carcinoid tumor in Meckel's diverticulum. The Meckel's diverticulum is a congenital abnormality arising from a patent vitelline duct and is found at the anti-mesenteric side of the ileum. In the Meckel's diverticulum, ectopic tissue or neoplasms are sometimes found, which may lead to intussusception, hemorrhage, or inflammation. The carcinoid tumor is a neuroendocrine neoplasm originating from the neural crest and is diagnosed at virtually all ages. It may exhibit malignant behavior but generally has a mild clinical course. It is most often found in endodermally derived organs, especially the digestive and pulmonary tracts, and coexists frequently with malignant tumors, predominantly of endodermal origin such as colorectal carcinoma. The carcinoid tumor and Meckel's diverticulum are known to coincide, whereas the carcinoid is not really considered to be an embryologically determined defect. We hypothesize that both lesions are derived from local erroneous interaction among the neural crest and the endoderm.