Endoscopic resection of poorly differentiated adenocarcinoma arising from hyperplastic polyp

Abstract

A 64-year-old male patient underwent several endogastroduodenoscopy (EGD) procedures for treatment of multiple gastric hyperplastic polyps. An erosion (2×3mm) was observed on a hyperplastic polyp located in the antrum at the greater curvature of the stomach. Magnifying endoscopy with narrow band imaging (NBI) revealed that superficial formation and fine network pattern of the mucosa had disappeared. This lesion was diagnosed by pathological assessment of a biopsy specimen as adenocarcinoma, including a poorly differentiated component. Although poorly differentiated carcinoma was involved, we elected endoscopic submucosal dissection (ESD) because the cancer was thought to be contained within 20mm mucosal depth. Histopathological analysis of the ESD specimen revealed horizontal and vertical margins of the cancer were negative, but lymphovascular involvement was present. Therefore additional surgical resection was performed. Lymph-node metastasis and residual cancer were not detected. Carcinogenicity of hyperplastic polyps is unknown at present, but recently several cases of poorly differentiated adenocarcinoma developing in hyperplastic polyps have been reported. These polyps were frequently discovered extending deeper than 20mm. In the case reported here, a poorly differentiated adenocarcinoma developed in a hyperplastic polyp less than 10mm in depth and required additional surgical resection. We conclude that it is necessary to monitor hyperplastic polyps strictly regardless of size, especially in cases with existing risks of carcinogenesis such as H. pylori infection and non-uniform or recess type polyp.