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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.
THE AMERICAN CANCER SOCIETY estimates that 19,500 new cases of thyroid cancer are diagnosed and 1300 thyroid cancer-related deaths occur each year in the United States.1 Four types of thyroid cancer comprise more than 98 per cent of all thyroid malignancies.2 Well-differentiated papillary and follicular tumors are associated with a good prognosis, whereas Hurthle cell tumors, which are usually classified as variants of follicular carcinoma, tend to be more aggressive. Medullary and anaplastic (undifferentiated) tumors are associated with a much poorer prognosis, with anaplastic thyroid carcinoma recognized as among the most aggressive human malignancies.2
The initial treatment of thyroid carcinoma depends on the tumor type. For localized tumors, treatment options include surgery with or without radioactive iodine therapy (or external radiation) followed by suppression of serum thyrotropin concentrations.2-3 However, the optimal treatment regimen is debated, including the extent of primary surgical resection, the role of lymph node dissection and postoperative radioactive iodine remnant ablation, and the degree of suppression of thyrotropin needed in long-term management.4 Spread of undifferentiated or medullary thyroid cancer to distant organs has virtually no efficacious therapy.
Several gene mutations have been associated with the pathogenesis of thyroid carcinomas. These include somatic RAS mutations in follicular thyroid carcinomas, somatic rearrangements of RET and TRK in papillary...