HER2 expression in thyroid tumors.

Similarities exist in hormone receptors of breast, prostate, and thyroid tumors. HER2 oncogene expression is known to be present in breast and prostate tumors, but conflicting data have been published about its presence in thyroid tumors. This uncertainty prompted us to examine the incidence of HER2 overexpression in normal and malignant thyroid tissue. Normal and neoplastic thyroid tissue samples from 46 female and 9 male patients were assayed for HER2 expression by immunohistochemical assay. Of the 55 total samples, 36 were from neoplasms and 19 were from benign tissues. Significant HER2 overexpression was not found in any benign or malignant thyroid tissue. Two of 6 thyroid carcinomas from male patients showed 1+ reactivity for HER2 expression on immunohistochemistry assay, but remained negative on fluorescene in sito hybridization confirmatory testing. No significant expression of HER2 was noted in benign or malignant thyroid tissue. These results cast doubt on the value of HER2 as a prognostic factor or possible target for specific antitumor therapy for thyroid cancer.