Immunohistochemistry Differentiates Papillary Thyroid Carcinoma Arising in Ectopic Thyroid Tissue from Secondary Lymph Node Metastases

Objective: To verify whether immunohistochemistry might be useful in the distinction between a true laterocervical metastasis of an undetected thyroid carcinoma and a primary tumor outside the gland. Design: Galectin-3, cytokeratin 19, and HBME-1 were assessed in six cases (group A) of laterocervical masses harboring papillary thyroid carcinoma (PTC) but without a thyroid tumor, and in eight cases (group B) showing PTC both in the thyroid and in the laterocervical masses. In both groups, normal-looking follicles adjacent to the laterocervical neoplasia were present. Main outcome: We found that the apparently normal follicles in group A were negative for all the antibodies, while group B sho…