Endometrioid tumor

Endometrioid tumors are a class of tumor characterized by a resemblance to endometrium/ endometrial carcinoma, and over a third of cases have focal squamous differentiation.

Ovary
They are part of the surface epithelial tumor group of ovarian neoplasms (10–20% of which are the endometrioid type). Benign and borderline variants are rare, as the majority are malignant. There is an association with endometriosis and concurrent primary endometrial carcinoma (endometrial cancer).

On gross pathological examination, the tumor is cystic and may be solid and some arise in cystic endometriosis. In 40% of cases, endometrioid tumors are found bilaterally.

Endometrium
Endometrioid carcinoma can also arise in the endometrium.

Grades 1 and 2 are considered "type 1" endometrial cancer, while grade 3 is considered "type 2".