Inclusion Criteria:  Patients with endoscopically diagnosed and endosonographically confirmed submucosal tumors of 0.5 to 2 cm in the stomach without definitive histology / cytology Initial diagnosis less than 2 years ago No contraindication to endoscopic resection Patient's informed consent  Exclusion Criteria:  Tumor size > 2 cm Tumors with proven / suspected malignancy for which oncologically no endoscopic resection should be performed, i.e. for which oncological or surgical therapy is planned SMT known > 2 Years Patients with severe general illnesses (limited operability) or malignancies Clotting disorders Pregnancy