Gastric neuroendocrine neoplasms: A review

Abstract

Gastric neuroendocrine neoplasms (g-NENs) or neuroendocrine tumors are generally slow-growing tumors with increasing incidence. They arise from enterochromaffin like cells and are divided into four types according to clinical characteristic features. Type 1 and 2 are gastrin dependent, whereas type 3 and 4 are sporadic. The reason for hypergastrinemia is atrophic gastritis in type 1, and gastrin releasing tumor (gastrinoma) in type 2 g-NEN. The diagnosis of g-NENs needs histopathological investigation taken by upper gastrointestinal endoscopy. g-NENs are positively stained with chomogranin A and synaptophysin. Grading is made with mitotic index and ki-67 proliferation index on histopathological analysis. It is crucial to discriminate between types of g-NENs, because the management, treatment and prognosis differ significantly between subtypes. Treatment options for g-NENs include endoscopic resection, surgical resection with or without antrectomy, medical treatment with somatostatin analogues, netazepide or chemotherapy regimens. Follow-up without excision is another option in appropriate cases. The prognosis of type 1 and 2 g-NENs are good, whereas the prognosis of type 3 and 4 g-NENs are close to the prognosis of gastric adenocancer.

Gastric neuroendocrine neoplasms and precursor lesions

“…Tumor has non-ECL origin and is not associated with autoimmune gastritis or gastrinoma, being gastrin-independent. Tumor is large (>4 cm), located anywhere in the stomach, [ 8 , 15 , 38 ] showing positive immunostaining with synaptophysin and cytosol markers NSE and PGP9.5, while chromogranin A is absent or focally expressed. [ 16 , 39 ] According to the recent WHO classification system, tumor is a NEC, with aggressive behaviour, vascular invasion, and metastases.…”

Type-1 Grade 2 Multi-Focal Gastric Neuroendocrine Tumors Secondary to Chronic Autoimmune Gastritis

“…Normally, for chronic autoimmune gastritis (CAG), women would have a higher prevalence with a 3:1 ratio to males (2,4). The research found that the histologic change in CAG is a risk factor for gastric neuroendocrine tumor (G-NET) development (5,6), and in patients with CAG, the annual incidence of G-NET was 0.68% per person-year (7,8).…”

“…Type-1 G-NETs predominantly occurred in females, representing 70-80% of G-NETs, and are gastrin-dependent (10). Normally, type-1 G-NETs are small multiple tumors around 1-2 cm located in the gastric body or fundus (6,9,11). Type-2 G-NETs take up 5% of the G-NETs.…”

“…They are also small and multiple tumors but have an equal prevalence in males and females FIGURE 1 | Routine gastroscopy revealed smooth mucosa in the gastric antrum (A), absence of gastric fold along the greater curvature of the gastric body (B), pale appearance of mucosa, increased visibility of vasculature, and multiple gastric submucosal bulges within gastric body, and fundus (B,C), EUS confirmed hyperechoic NETs originated from the muscularis mucosa, with an intact muscularis propria (D). (6,(9)(10)(11). Type-3 G-NETs comprise 10-15% of the G-NETs and are more frequently found in males.…”

“…They are normally single and larger than 1 cm, with high metastasis potential. In total, 25-40% of Type-3 G-NETs are malignant (6,9,10). The newly defined and rarest Type-4 G-NETs are also sporadic and gastrin-independent but with the highest metastasis potential (6,10).…”