Histopathological examination established metastatic high-grade serous carcinoma of Müllerian origin, with tumor cells positive for CK7, PAX8, P53 (diffuse and strong), and P16 (diffuse and strong), while negative for CK20, CDX2, TTF1, and GATA3 (Fig. 3). The gene discussed is CDX2; the disease is serous adenocarcinoma.