MUCINOUS ADENOCARCINOMA ARISING IN A GIANT URACHAL CYST ASSOCIATED WITH PSEUDOMYXOMA PERITONEI AND STROMAL OSSEOUS METAPLASIA

An unusual urachal lesion, which is a mucinous adenocarcinoma arising in a giant urachal cyst and is associated with pseudomyxoma peritonei and stromal osseous metaplasia of the cyst wall, was examined in a 45- year-old male. The cyst was encapsulated, measured 22x20x20 cm and wei ghed 3800 g. The unilocular cavity was filled with mucin. Most of the cystic cavity was lined with tall, simple or stratified columnar epith elium with a focus of papillary projection into the cavity. These find ings suggest that this cystic lesion represents cystadenoma rather tha n a simple cyst. Foci of invasive moderately differentiated mucinous a denocarcinoma were detected in the area of macroscopic papillary frond s. Carcinoembryonic antigen and CA19-9 were immunohistochemically posi tive for tumor cells and their serum levels were also elevated. Stroma l dystrophic calcification was extensively observed in the cyst wall w ith foci of osseous metaplasia. Mucinous implants, which histologicall y demonstrated adherent mucinous masses without epithelial components on the surface, were observed in the pelvic and abdominal cavity, indi cating pseudomyxoma peritonei.