Inclusion Criteria:  Patients who are diagnosed with undifferentiated type EGC (signet ring cell carcinoma, poorly differentiated tubular adenocarcinoma, or poorly cohesive carcinoma) that meets the expanded indication of ESD 1) Tumor confined to the mucosa without ulcer, and size ≤2 cm on endoscopic evaluations 2) No evidence of lymph node metastasis and distant metastasis on abdominal CT scan Adult patients aged 19-75 years Patients who had willingness to sign an informed consent form  Exclusion Criteria:  Patient age: < 19 years or age > 75 years Diagnosis and active treatment for other organ cancer except carcinoma in situ and non-melanomatous skin cancer within 5 years Previous gastrectomy or esophagectomy history Multiple gastric cancers Current treatment for serious medical condition which could hinder study participation including severe heart dysfunction, liver cirrhosis, renal failure, chronic obstructive pulmonary disease or asthma, or uncontrolled infection Inability to provide an informed consent Inadequate conditions for study enrollment according to the evaluation of study physicians