Loss of estrogen receptor β expression in follicular thyroid carcinoma predicts poor outcome.

Background: Well-differentiated follicular thyroid carcinomas (FTCs) usually act indolently, while aggressively acting tumours are difficult to detect early enough. Estrogen receptors (ERs) have prognostic significance in many cancers. Thyroid diseases, including neoplasms, are associated with the female sex. The prognostic significance of ERs in FTCs has not been reported previously. Methods: We studied the role of ERα and ERβ in 83 follicular thyroid adenomas (FTAs) and 43 FTCs, including seven poorly differentiated FTCs, obtained from the Department of Surgery, Helsinki University Central Hospital between 1990 and 2009. Patient follow-up was conducted until March 2011. Expression of ERα, ERβ and MIB-1/Ki-67 was investigated by immunohistochemistry and correlated with clinicopathological characteristics, including survival. Results: Two major observations were apparent. First, ERβ expression was significantly higher in FTAs than in FTCs, and it was a stronger differential diagnostic marker than MIB-1/Ki-67. Second, low ERβ expression correlated with poor survival in FTCs. All cancer-specific deaths due to FTC were among low ERβ-score patients. Conclusion: ERβ is a differential marker for malignancy and could thus be used as a preoperative tool. FTC patients with a low ERβ score need more thorough follow-up and may benefit from more aggressive treatment.