Immunohistochemistry showed that the malignant cells were positive for PAX8 (Figure 4A,B) and WT1 (Figure 4A), negative for the mesothelial marker, calretinin (Figure 4A), p53 mutation pattern (Figure 4A, abnormal strong diffuse expression), and p53 null pattern (Figure 4B), consistent with a high-grade serous carcinoma of ovarian primary origin of both cases. The gene discussed is PAX8; the disease is serous adenocarcinoma.