Neuroendocrine tumor

Neuroendocrine tumors are rare (<1% of all malignancies), mostly in the GI tract and pancreas. Carcinoid is the most common, incidence ~2.5/100,000, accounting for 50% of GI-pancreatic NETs. By origin: foregut (lung, bronchi, upper GI to jejunum), midgut (ileum, appendix), hindgut (rectum). They can occur throughout the neuroendocrine system but most commonly involve the pancreas. By function: functional vs nonfunctional.

Common Symptoms

Painful red tongue; chapped lips; steatorrhea; thrombocytopenia; achlorhydria

Causes

Etiology unknown; some hereditary. Offspring of NET patients have ~50% risk, so screening is important. MEN-IIA/IIB genes identified. NETs (APUDomas) produce small polypeptides/peptide hormones: serotonin (5-HT), kallikrein, histamine, ACTH, catecholamines, GH, PTH, calcitonin, ADH, gonadotropins, insulin, glucagon, prostaglandins, gastrin, motilin. Carcinoid syndrome is mainly due to serotonin and bradykinin. Serotonin constricts peripheral/pulmonary vessels and bronchi, stimulates GI vagus/ganglia. Bradykinin is a potent vasodilator; gastric carcinoids produce lots of bradykinin/histamine causing flushing; high circulating serotonin causes endocardial fibrosis. Normally only ~2% of dietary tryptophan makes 5-HT, but in carcinoid syndrome ~60% is taken up by tumor cells, increasing 5-HT and reducing niacin. Most free 5-HT is metabolized by MAO in liver/lung/brain to 5-HIAA excreted in urine. Midgut carcinoids: high serum 5-HT and urinary 5-HIAA (typical, ~75% of cases). Foregut carcinoids lack DOPA decarboxylase, so 5-HTP is released directly (atypical syndrome).

Treatment

Surgery; drug therapy; supportive care

Prevention

Hereditary; early screening important. Hematogenous/lymphatic multiple skin metastases indicate late disease with survival 3-12 months.

Recommended Department

It is recommended to visit the oncology department; before the visit you may first book an appointment and connect with experts through this platform.

Warm reminder: The above information is provided for health education reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek care at a regular hospital in time.