Endocrine Abstracts

Introduction: The role of F-18 FDG PET/CT in follow-up of differentiated thyroid cancer (DTC) is well established. Molecular markers were shown to be related with malignancy risk of thyroid nodules and prognosis of DTC. The goal of this study was to assess the relation of molecular markers such as NIS, Galectin-3, PTEN, Ki-67, p53 with PET positivity and malignancy of thyroid.

Methods/design: We evaluated patients who had 18-FDG uptake in thyroid gland at F-18 FDG PET/CT and subsequently underwent total thyroidectomy. Pathology and PET-CT reports were investigated retrospectively. Fifteen patients with 27 nodules who had FDG uptake in thyroid were included. Twenty-one nodules were PET positive. Thirteen nodules were malignant and eight were benign. Six malignant nodules of these patients without 18-FDG uptake were also included. Immunohistochemical staining with Galectin-3, NIS, PTEN, p53 andKi67 in surgical specimens was performed.

Results: Six out of eight benign nodules (75%) were not stained with Galectin-3 and seven (36.8%) of malignant nodules had negative Galectin-3 staining. Twelve nodules stained moderately intense or intense with Galectin-3. NIS expression was frequent and intense in elder people. Loss of PTEN expression was frequent in malignant nodules. PTEN staining was not seen in 42.1% (n:8) of malignant and 12.5% (n:1) of benign nodules. Nodules were not stained for p53.F-18 FDG positivity in malignant and benign nodules was not associated with Galectin-3, NIS, Ki67 or PTEN expression.

Conclusion: FDG-PET positivity and malignancy risk were not associated with Galectin-3, NIS, Ki67, PTEN and p53 expression. New studies are necessary for explaining pathogenesis and role of molecular markers in development of FDG-PET positive thyroid nodules.