Figure 1. Histological and immunophenotypical examination of the resected specimen. (a) Hematoxilin and Eosin staining of the specimen, with clear delineation of native thyroid tissue and metastatic neoplastic disease, thyroid colloid depicted by red arrow. (b) Increased magnification of (a), again with red arrow depicting native thyroid colloid. (c) Immunohistological staining of specimen with anti-CK20 antibodies and (d) with anti-CDX-2 antibodies, suggesting the diagnosis of metastatic colon cancer to the thyroid.