Ovarian mucinous tumors range from benign cystadenomas to borderline tumors to frankly malignant adenocarcinomas, and may display either intestinal-type morphology or, less frequently, endocervical-type differentiation. The latter category has been the subject of recent controversy owing to its morphologic overlap with so-called "seromucinous" ovarian tumors, a group that shares more molecular features with endometrioid tumors than it does with either serous or mucinous ovarian neoplasias. Endocervical-type differentiation in ovarian mucinous tumors may also represent an endocervical metastasis. Distinction of primary ovarian mucinous tumors from gastrointestinal metastases can be difficult, as the morphology of intestinal-type ovarian mucinous primaries sometimes differs only subtly if at all from gastrointestinal metastases.