Distribution of GPER immunohistochemical staining in serous, mucinous and endometrioid ovarian tumors Altogether 37 samples were evaluated. Abbreviations are as in Figure 1. Non-immune IgG replaced the GPER antibody as a negative control (NC). Staining was mainly localized in tumor cells, but also in single stromal cells. It tended to be strongest in tumor cells close to the stroma. Staining could be identified both in cell membranes and in the cytoplasm.