Borderline-like mucinous tumor arising in mature cystic teratoma of the ovary associated with pseudomyxoma peritonei.

Pseudomyxoma peritonei (PMP) is now considered to originate from appendiceal mucinous neoplasms in almost all cases. However, a mucinous neoplasm arising in a mature cystic teratoma is rarely responsible for PMP. We herein report 2 cases of PMP associated with borderline mucinous tumors arising in mature cystic teratoma. Both ovarian borderline mucinous tumors were morphologically and immunohistochemically similar to the secondary tumors from appendiceal origin, and PMP was histologically similar to peritoneal adenomucinosis.