Metastatic adenocarcinoma of the lung (TTF1+, napsin A+, PAX8-), colorectal carcinoma (β-catenin+, CDX2+, CK20+, SATB2+, PAX8-, and often TTF1-) or endometrial carcinoma (PAX8+, often TTF1-) can also simulate primary thyroid carcinomas (with a papillary and/or follicular pattern), but metastatic carcinomas are all negative for thyroglobulin [2, 112, 117] (Fig. 9a-f). The gene discussed is TTF1; the disease is endometrial carcinoma.