Proliferative endometrioid tumors and endometrioid tumors of low malignant potential of the ovary.

Endometrioid epithelial tumors occur as adenofibromas, proliferative endometrioid tumors, endometrioid tumors of low malignant potential, and endometrioid carcinoma. Criteria for each category are given. Proliferative endometrioid tumors are benign, and the low-malignant-potential ones seldom, if ever, metastasize; they should not be designated carcinomas or regarded as malignant. However, invasive carcinoma may arise in both, and both may be associated with a similar tumor outside ovary, the latter a result of either a second primary neoplasm or rupture of the primary ovarian tumor. Endometrioid tumors of low malignant potential do not need a staging procedure. Their behavior is more akin to that of Brenner and mucinous tumors of low malignant potential than to that of serous tumors of low malignant potential. Vague terms such as "malignant adenofibroma" and "borderline endometrioid tumor" have been attached to a variety of intermediate endometrioid neoplasms and should be dropped in favor of more specific designations defined by semiquantitative criteria.