A 77-year-old male underwent gastroscopy in our institution. Conventional endoscopic examination revealed two ectopic gastric mucosas (EGMs) located about 17cm from the incisors. One of the EGMs was about 0.6cm in size and was round with a flat surface and a slight uplift in the center. The boundary of the uplift was clear and the villous structure disappeared. Narrow Band Imaging (NBI) showed irregular microvessels with a fine network pattern at the uplift, and there appeared to be small and punctate crypt opening (CO) in the glandular ducts. Then we performed acetic acid staining and found that the lesion showed dense and small CO clearly, suggesting differentiated gastric cancer. Histopathologic diagnosis of the biopsy specimen from the lesion was high-grade intraepithelial neoplasia.