B7-H4 protein expression in normal ovary (A), fallopian tube (B), and high-grade ovarian serous carcinoma (C-F). B7-H4 immunohistochemical staining in ovarian serous carcinoma was semi-quantified using a four-score grading system: Score 0 (C), negative; Score 1 (D), apical pattern; Score 2 (E), mixed apical and circumferential membranous staining with circumferential membranous staining in <10% of tumor cells; Score 3 (F), circumferential membranous staining in ≥10% of tumor cells (immunohistochemical stain; original magnification ×200).