1. ¹Endocrine Unit, Division of Endocrinology and Diabetes, Department of Medicine, University Hospital Geneva, Geneva, Switzerland
2. ²Division of Clinical Pathology, Department of Pathology, University Hospital Geneva, Geneva, Switzerland
3. ³Clinic of Thoracic Surgery, Department of Surgery, University Hospital Geneva, Geneva, Switzerland
4. ⁴Department of General Surgery and Transplantation, University Hospital Essen, Essen, Germany
5. ⁵Institute of Pathology, University Hospital Essen, Essen, Germany

Correspondence: Christoph A. Meier, M.D., Endocrine Unit, University Hospital Geneva, 24, Rue Micheli-du-Crest, CH–1211 Geneva 14, Switzerland; fax: 41-22-372-9330; e-mail: christoph.meier@hcuge.ch

Accepted 15 August 2003.

Abstract

Galectin-3 has been extensively studied as an immunohistochemical marker of thyroid malignancy, and a high diagnostic accuracy has been reported even for difficult pathological diagnoses, such as minimal invasive follicular carcinoma. We consequently hypothesized that the quantitative analysis of galectin-3 mRNA rather than the more observer-dependent immunohistological determination might enhance the diagnostic workup of ambiguous thyroid lesions. In the present study, we set out to validate this approach by analyzing concomitantly the expression and production of galectin-3 in benign and malignant thyroid tumors by means of quantitative PCR and immunohistochemistry. Twenty-eight benign and 31 malignant thyroid samples were quantified by real-time PCR for the mRNA levels of galectin-3 and thyroglobulin. Galectin-3 protein expression was examined by immunohistochemistry in 13 benign and 14 malignant thyroid samples. There was a significant increase in galectin-3 at both the mRNA (12/20) and protein levels in papillary cancer (8/8), although the mRNA values overlapped partly with benign lesions. Surprisingly, only a focal and discrete galectin-3 immunoreactivity was seen in follicular cancer (1/5); no augmentation of the mRNA was found. The expression of the thyroid-specific gene thyroglobulin was highly variable in benign and malignant thyroid tissue. These results suggest that the quantitative measurement of galactin-3 mRNA is unlikely to be clinically useful and underscore the need for searching for novel markers for thyroid malignancies.