Duodenal Neuroendocrine Tumors

Duodenal NETs are rare and represent < 2% of all gastrointestinal NETs. Five major types of NETs are identifiable in the duodenum.10 Gastrin-producing tumors are most frequent (Figure 18-6). Most of the remaining tumors are rich in somatostatin, but tumors with increased serotonin production or other peptides also exist.50 Only 92 cases of duodenal somatostatinomas have been reported in the English literature. Their designation as somatostatinomas is made on the basis of immunohistochemical staining. An important association exists between duodenal NETs and von Recklinghausen's disease. Almost 90% of duodenal NETs in patients with von Reck-linghausen's disease are pure yet nonfunctioning somatostatinomas. They seem to have a predilection for the ampulla of Vater. By contrast, duodenal NETs not associated with von Recklinghausen's disease are frequently multihormonal.55 Gangliocytic paragangliomas are predominantly immunohisto-chemically somatostatin and pancreatic polypeptide positive and usually behave in a benign fashion. Tumors secreting serotonin, calcitonin, or pancreatic

Gastrin producing tumors (60%)

1/3 functioning tumors 2/3 nonfunctioning tumors

Everywhere Duodenal bulb

Somatostatin-producing tumors (20%) Ampulla of Vater

1/3 associated with von Recklinghausen's disease

Gangliocytic paragangliomas

Poorly differentiated

Neuroendocrine carcinoma

Duodenal NET producing

Serotonin, PP, or cacitonin

Ampullary region

Ampulla of Vater

Outside of the Ampulla of Vater

Figure 18-6. Distribution and location of duodenal neuroendocrine tumors (NETs). PP = pancreatic polypeptide.

polypeptide are very rare. Lastly, poorly differentiated neuroendocrine carcinomas are extremely rare and highly aggressive tumors.10 Duodenal NETs are thought to be composed of cells with endocrine differentiation coming from duodenal mucosa. Carcinoid syndrome is rare with duodenal NETs.10 The management of these lesions is determined on a case-by-case basis and is dictated by the presence of symptoms.55,56 Negative prognosis features include tumor size > 2 cm, involvement of the muscularis propria, the presence of mitotic figures, and local or distant metastases.10

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