After the borders of the tumor were marked, a 0.9% saline solution with indigo carmine and epinephrine was injected in the submucosal layer. Circumferential mucosal incision and submucosal dissection were then performed using a dual knife and an insulated-tipped knife. During dissection, a clip attached with dental floss was used to secure the dissection plane between the tumor and the proper muscle layer (Fig. 1C). The tumor was then completely resected (Fig. 1D).

Histopathological examination revealed that the cystic invagination of the mucosal lesion was composed of neoplastic glands with high-grade dysplasia. Most of the glandular cells had round nuclei with prominent nucleoli and mucinous columnar cytoplasm that resemble the pyloric glandular epithelium (Fig. 2). Therefore, the lesion was diagnosed as an inverted pyloric gland adenoma with high-grade dysplasia.

Pyloric gland adenoma is a rare neoplasm, and the histological resemblance of the tumor to the deep glands of the gastric mucosa near the pylorus is reflected in its name [1]. It occurs more frequently in women and in the elderly. As adenocarcinoma is detected in approximately 30% of pyloric gland adenomas [2], they are considered precancerous lesions, and endoscopic removal is indicated [3]. As described in our report, ESD using dental floss and clip traction seems to be an efficient and safe technique for inverted pyloric gland adenomas, especially when the tumor is located in the greater curvature of the upper or middle stomach [4].