Copyright ©The Author(s) 2021.
World J Clin Cases. Sep 26, 2021; 9(27): 7973-7985
Published online Sep 26, 2021. doi: 10.12998/wjcc.v9.i27.7973
Table 1 Classification of neuroendocrine neoplasms according to World Health Organization criteria

Mitotic rate (mitoses/mm2)
Ki-67 index
Neuroendocrine tumor, Grade 1< 2< 3%Well
Neuroendocrine tumor, Grade 22-203%-20%Well
Neuroendocrine tumor, Grade 3> 20> 20%Well
Neuroendocrine carcinoma, small-cell type> 20> 20%Poor
Neuroendocrine carcinoma, large-cell type> 20> 20%Poor
Mixed neuroendocrine–non-neuroendocrine neoplasmVariableVariableVariable
Table 2 Characteristics of the subtypes of neuroendocrine neoplasms of the stomach

Type 1
Type 2
Type 3
Type 4
Approximate Proportion 70%-80%5%10%-25%Rarely
PathogenesisIncreased gastrin levels due to atrophic gastritis. ECL originIncreased gastrin levels due to gastrinoma. ECL originNot known. Mostly ECL originNot known. Non-ECL origin
Location and characteristicsGastric body and fundus. Often small and multipleGastric body and fundus. Often small and multipleAnywhere. Large and solitaryAnywhere. Large (often larger than type 3)
Gastrin levelIncreasedIncreasedNormalIncreased or normal
TreatmentSurveillance without resection, Endoscopic resection, surgeryEndoscopic or surgical resection, resection of gastrinomaGastrectomy and regional lymphadenectomy, systemic chemotherapyGastrectomy and regional lymphadenectomy, systemic chemotherapy