PAX8 and ovarian neoplasm: PAX8 positivity has also been demonstrated in several cases of renal, thyroid, and ovarian tumors [7-12]. Due to its high sensitivity and absence of expression in breast, lung, gastrointestinal, and mesothelial malignancies, PAX8 immunohistochemistry is now routinely used as an adjunctive tool in diagnosing tumors, especially when they become metastatic [10, 12-14].