Small G1 type III gastric neuroendocrine cell tumor showing scirrhous invasion and lymph node metastasis

Abstract

A 42-year-old woman underwent upper endoscopy for screening. EGD revealed a raised lesion with a central depression in the lesser curvature of the lower body of the stomach (A). Magnified endoscopy with narrow-band imaging showed that most of the surface of the tumor had a normal pattern. However, in the central depression, the pit structures were disappearing, the microvessel image was slightly irregular, and dilatated cyan subepithelial vessels were seen there with magnified endoscopy with narrow-band imaging (B). The biopsy result revealed a gastric neuroendocrine tumor (NET). The serum gastrin level was 116 pg/mL, and test results for antiparietal cell antibody and Helicobacter pylori infection were negative. Therefore, the NET was diagnosed as a type III gastric NET. We performed endoscopic submucosal dissection for the tumor. However, the tumor was adhered to the muscle layer; therefore, it was difficult to dissect the tumor (C). The tumor diameter was 8 mm. NET was observed in the mucosa and submucosa (D, H&E, org. mag. ×100); in particular, the tumor cells infiltrated into the submucosa with strong fibrosis, like scirrhous (E, H&E, org. mag. ×100, F, α-smooth muscle actin, orig. mag. ×100), resulting in incomplete resection. Notably, the Ki67 index of the tumor was 2%; therefore, this tumor was classified as NET G1. Additional surgical resection revealed no residual tumor; however, 2 lymph node metastases were observed.