The tumors excrete serotonin and other hormonally active compounds which can lead to the carcinoid syndrome. Carcinoid syndrome can therefore suggest the presence of metastasis to non- GI locations.
Tumor invades the submucosa and muscularis.
In extra appendiceal sites it frequently penetrates the bowel wall. Miscellaneous Carcinoids are the most common primary neoplasms of the small intestine. They can be located anywhere in the GI tract, bronchi, biliary tract, and pancreas. Imaging Primary carcinoids are often not visualized on CT exam. Sometimes they appear as soft tissue masses associated with the bowel wall.