GATA6 and atypical endometrial hyperplasia: This event is accompanied by a reciprocal increase in GATA6. Here, we applied custom anti-GATA2 monoclonal antibodies and performed GATA2 immunohistochemistry (IHC) on patient endometrial tissues corresponding to proliferative, secretory, inactive, and hormone-treated endometrium, as well as endometriosis and endometrial atypical hyperplasia/endometrioid intraepithelial neoplasia (EAH/EIN).