Mucoceles of the appendix. Their relationship to hyperplastic polyps, mucinous cystadenomas, and cystadenocarcinomas.

Sixty-four cases of hyperplastic polyp, mucinous cystadenoma, and cystadenocarcinoma of the appendix were studied in relation to the development of mucocele and "pseudomyxoma peritonei." Thirty-three cases were examples of hyperplastic polyps. In 11, the appendix was transformed into a mucocele; eight were associated with mucinous cystadenoma and one with mucinous cystadenocarcinoma. The hyperplastic polyp alone was the cause of mucocele formation in two. Thirty-five cases represented examples of mucinous cystadenoma; 32 resulted in mucocele formation. Rupture with localized pseudomyxoma peritonei was found in six; generalized pseudomyxoma peritonei was encountered only once. In four of the five cases of mucinous cystadenocarcinoma, the appendix was grossly transformed into mucoceles. The histological features of mucinous cystadenoma are identical to villous adenoma of the large bowel and probably represent its counterpart within the appendix.