The finding of gastric dysplasia not associated with macroscopic lesions (DNAML) or the follow-up of dysplasia after endoscopic resection (DAER) is a challenging dilemma. In the last few years, radiofrequency ablation (RFA) has become a recognized tool in the treatment of dysplastic Barrett's esophagus, but its use in gastric dysplasia has not yet been studied. The investigators aim to study the efficacy, safety and tolerability of RFA in the treatment of dysplastic gastric mucosa.