Skip to Main Content

Chapter 80: Neuroendocrine Tumors of the Gastrointestinal Tract and Pancreas

Robert T. Jensen

GENERAL FEATURES OF GASTROINTESTINAL NEUROENDOCRINE TUMORS

Gastrointestinal (GI) neuroendocrine tumors (NETs) are tumors derived from the diffuse neuroendocrine system of the GI tract, which is composed of amine- and acid-producing cells with different hormonal profiles, depending on the site of origin. NETs of the GI tract share many features with other NETs throughout the body and were historically divided into GI-NETs (in the GI tract) (also frequently called carcinoid tumors) and pancreatic neuroendocrine tumors (pNETs), although in newer pathologic classifications they are all classified as NETs (Table 80-1). These tumors originally were classified as APUDomas (for amine precursor uptake and decarboxylation), as were pheochromocytomas, NETs in other locations, melanomas, and medullary thyroid carcinomas, because they share certain cytochemical features as well as various pathologic, biologic, and molecular features. It was originally proposed that APUDomas had a similar embryonic origin from neural crest cells, but it is now known that the peptide-secreting cells are not of neuroectodermal origin.

TABLE 80-1Comparison of the Criteria for the Tumor Category in the ENETS AJCC TNM Classifications of Pancreatic and Appendiceal NETs (Top Panel) and the WHO/ENETS Grading and Classification (Bottom Panel)
View Table||Download (.pdf)
TABLE 80-1 Comparison of the Criteria for the Tumor Category in the ENETS AJCC TNM Classifications of Pancreatic and Appendiceal NETs (Top Panel) and the WHO/ENETS Grading and Classification (Bottom Panel)
A. TNM Classification
  ENETS TNM AJCC/UICC TNM
pNETs    
T1 Confined to pancreas, <2 cm Confined to pancreas, <2 cm
T2 Confined to pancreas, 2–4 cm Confined to pancreas, >2 cm
T3 Confined to pancreas, >4 cm, or invasion of duodenum or bile duct Peripancreatic spread, but without major vascular invasion (truncus coeliacus, superior mesenteric artery)
T4 Invasion of adjacent organs or major vessels Major vascular invasion
Appendiceal NETs
T1 ≤1 cm; invasion of muscularis propria T1a, ≤1 cm; T1b, >1–2 cm
T2 ≤2 cm and <3 mm invasion of subserosa/mesoappendix >2–4 cm or invasion of cecum
T3 >2 cm or >3 mm invasion of subserosa/mesoappendix >4 cm or invasion of ileum
T4 Invasion of peritoneum/other organs Invasion of peritoneum/other organs

Abbreviations: AJCC, American Joint Committee on Cancer; ENETS, European Neuroendocrine Tumor Society; NET, neuroendocrine tumor; pNET, pancreatic neuroendocrine tumor; TNM, tumor, node, metastasis; UICC, International Union Against Cancer.

Source: Modified from DS Klimstra: Semin Oncol 40:23, 2013 and G Kloppel et al: Virchow Arch 456:595, 2010.

View Table||Download (.pdf)
B. Grading
CLASSIFICATION GRADE MITOTIC COUNT (PER 10 HPF) KI67 INDEX (%)
NET G1 <2 ≤2
NET G2 2–20 3–20
NEC (small cell and large cell) G3 >20 >20

Abbreviations: HPF, high-power field; NEC, neuroendocrine carcinoma; NET, neuroendocrine tumor.

CLASSIFICATION/PATHOLOGY/TUMOR BIOLOGY OF NETs

NETs generally are composed of monotonous sheets of small round cells with uniform nuclei, and mitoses are uncommon. They can be frequently ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.

This site uses cookies to provide, maintain and improve your experience. MH Privacy Center Close