[1] They account for 80% of endometrial carcinomas[1]: 724  and 20% of malignant ovarian tumors.

Benign and borderline variants are rare, as the majority are malignant.

[6] Light microscopy shows tubular glands, resembling endometrium.

[8] Ovarian and endometrial endometrioid carcinomas have distinct CTNNB1 and PTEN gene mutation profiles.

This difference in CTNNB1 mutation frequency may be reflective of the distinct tumoral microenvironments; the epithelial cells lining an endometriotic cyst within the ovary are exposed to a highly oxidative environment that promotes tumorigenesis.