Two Cases of Gastric Adenocarcinoma with Enteroblastic Differentiation which Demonstrated Rapid Progressive Courses

We herein report two extremely rare cases of gastric adenocarcinoma with enteroblastic differentiation (GAED) that underscore the aggressive nature of GAED. Case 1: ESD was scheduled for early-stage gastric cancer, however, the tumor increased in size drastically and the morphology changed to type "0-I + IIc" in one month. Surgery was performed and the patient was diagnosed with GAED. Case 2: ESD was performed for early-stage gastric cancer, and the pathological findings revealed GAED. The horizontal margin was positive for clear cells in the muscularis mucosa. Additional surgery was performed; however, recurrence occurred one year later. Therefore, the treatment strategies should be carefully considered for GAED.