A mucocele of the appendix refers to distension due to the accumulation of mucinous material within the lumen, occurring due to obstruction of the lumen. While hyperplasia of the mucosa is a cause, neoplastic (both benign and malignant) appendiceal neoplasms are also a cause. In these latter cases, if the appendix ruptures, pseudomyxoma peritonei is a concerning outcome. For this reason, appendiceal mucoceles are removed.