Immunohistochemistry stains showed the tumor was positive for synaptophysin (Fig. 4C), chromogranin, INSM1, AE1/AE3, PAX8 (MRQ-50 clone) (Fig. 4D), CDX2 (patchy, weak), MOC31, and CD10 and was negative for claudin-4, CK7, CK20, GATA3, TTF1, p40, and S100; Ki-67 index was 1.5 %. The gene discussed is PAX8; the disease is neoplasm.