DISTINCTIVE FEATURES

Carcinoid tumors commonly occur in the bowel. However, these tumors also occur in the lungs, pancreas, salivary gland, breast, liver, and biliary tree.
Most commonly found in the sixth decade of life.
Tumors which arise in the appendix only infrequently metastasize. On the other hand, tumors which arise from the stomach, ileum or colon frequently are aggresive and mestastasize to the local lymph nodes and the liver.
These tumors are frequently asymptomatic. May produce bowel obstruction or bleeding. May produce various types of hormones and lead to the following:

Tumors that produce ACTH are associated with Cushing's syndrome.
Tumorst that produce gastrin are associated with multiple peptic ulcers which occur in the esophagus, stomach and small bowel (Zollinger Ellison syndrome).
Tumors that produce insulin are associated with signs and symptoms of hyperinsulinemia.
Tumors that produce serotonin and other bioactive amines are associated with carcinoid syndrome:

Vasomotor disturbances such as flushing and cyanosis, asthmatic symptoms such as wheezing, dyspnea and cough.
Hypermotility of the bowel associated with diarrhea, nausea, vomiting and abdominal cramps'.
Systemic fibrosis including retroperitoneal fibrosis, thickening and steonsis of the pulmonic and tricuspid valves, and pleural plaque.
Hepatomegaly due to hepatic metastasis.

The tumors may be diagnosed by demonstrating, increased urinary 5-hydroindolacetic acid (5-HIAA), the breakdown product of 5-hydroxytryptamine (5-HTor serotonin).