True pseudomyxoma peritonei is caused by:

In reality the pseudomyxoma peritonei or "jelly belly" probably represents mucinous ascites, in association with a cystadenoma of the appendix (resulting in true PMP); to frank mucinous adenocarcinoma. Additionally intestinal mucinous tumours, paicularly colorectal cancers, or any mucinous neoplasm may present with clinical, radiological and pathological features resembling pseudomyxoma peritonei. Ref: World J Gastrointest Oncol 2010 January 15; 2(1): 44-50.