PAX8 and thyroid gland carcinoma: In the case presentation above, the patient's tumor was positive for TTF-1 (could be seen in both thyroid and lung malignancy), Napsin-A (more commonly positive in lung malignancy but also seen in more poorly differentiated thyroid carcinomas), and PAX-8 (more commonly seen in thyroid malignancy), while it was negative for thyroglobulin.