A 42-year-old man presented with a submucosal tumor (SMT) -like elevated lesion with epithelial changes at the apex on the posterior wall of the fornix (lesion 1) as identified by esophagogastroduodenoscopy. He was referred to our hospital, and esophagogastroduodenoscopy revealed two more SMT-like elevated lesions, respectively located on the upper gastric body (lesion 2) and on the fornix (lesion 3). Cancer was not confirmed in any of the lesions despite three times biopsies. Based on the endoscopic findings, low-grade differentiated-type adenocarcinoma was suspected. A total gastrectomy was consequently performed. Histopathologic examination revealed that all lesions were low-grade differentiated-type adenocarcinoma, with lesions 1 and 2 identified as pyloric gland type gastric adenocarcinoma and lesion 3 identified as fundic gland mucosa type gastric adenocarcinoma. Low-grade differentiated-type adenocarcinoma can be difficult to diagnose using biopsy; therefore, it is necessary for endoscopists and pathologists to cooperate together to evaluate these lesions.