Appendiceal mucocele is a rare condition characterized by the obstructive enlargement of the appendix due to accumulation of mucin within its lumen[1-7].A 65-year-old patient following a positive fecal occult blood test underwent a colonoscopy that revealed a appendix's subepithelial tumor. A first CT scan confirmed the endoscopic suspicion.Subsequently, he was referred to our unit to perform ESD.The new colonoscopy showed a 2 cm subepithelial tumor, covered by normal mucosa with a single whitish erosion.Initially, the evaluation of the lesion's consistency was performed using foreign forceps, and when we pressed a large amount of mucus came out, with complete disappearance of the mass. Five weeks later, a second CT scan confirmed  the disappearance of the mucocele.