Molecular Pathology and Diagnostics of Thyroid and Parathyroid Malignancies

Abstract

Malignancies of the thyroid and parathyroid glands are rare oncologic entities that range in clinical behavior from relatively indolent to extremely aggressive malignancies. Presently, establishing a diagnosis and prognosis for thyroid and parathyroid malignancies largely depends on histology supplemented with immunohistochemical analysis. Over the past 20 years, different histologic subtypes of thyroid cancer have been shown to carry specific genetic alterations, which are often preferentially associated with, or unique to, each subtype. In many cases, these genetic alterations have been analyzed via molecular-genetic testing techniques to help establish a diagnosis in cases where histology and immunohistochemistry alone cannot. In addition, such testing has occasionally been used to determine prognosis. Presently, clinical molecular diagnostic testing is not performed on parathyroid tumors. However, differences between parathyroid hyperplasia, adenomas, and carcinomas have been detected via molecular testing. With additional research, these differences may become more fully understood and applied to molecular diagnostics. Thus, although presently not extensively employed, molecular diagnostics of the thyroid and parathyroid are likely to become increasingly important in determining the diagnosis and prognosis of these malignancies, especially for histologically difficult cases. Furthermore, pharmacologic inhibitors of many of the oncogenes mutated in these malignancies are being developed. With time, molecular diagnostic testing for these mutations is likely to be implemented to aid in choosing optimal chemotherapeutic treatment regimens.