Appendiceal mucinous cystadenoma associated with pseudomyxoma peritonei and multicystic peritoneal mesothelioma: Report of a case

An extremely rare case of mucinous cystadenoma developing to pseudomyxoma peritonei together with multicystic peritoneal mesothelioma is herein reported. The patient was a 25-year-old Japanese woman who underwent an appendectomy under the diagnosis of acute appendicitis because of right lower abdominal pain. The patient histopathologically demonstrated appendiceal mucocele with pseudomyxoma peritonei. She underwent a laparotomy in our unit following detailed examinations. Several cystic tumors measuring from 3 to 5 cm in diameter were found in the omentum, and thus omentectomy, partial cecectomy and left oophorectomy were all performed to resect the tumors. Immunostaining and electron microscopy showed the appendiceal lesion to be mucinous cystadenoma, while the peritoneal lesion was multicystic mesothelioma. To our knowledge, this is the first report in the world literature of this rare combination of diseases.