Seen here is a mucocele of the appendix in which the lumen is markedly dilated. It was filled with a clear, viscous mucoid material. These probably represent true neoplasms, most often a mucinous cystadenoma. Rupture of a mucocele can fill and distend the peritoneal cavity with mucin. Mucinous cystadenocarcinomas of appendix, colon, and ovary can also spread throughout the abdominal cavity and produce much the same pattern, except malignant cells are present, and the condition is known as pseudomyxoma peritonei.

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