Abstract
The aim of the present study was to investigate the expression of estrogen receptor β (ERβ) in triple-negative and triple-positive breast cancer patients, and evaluate its utility as a prognostic factor. Between January 2000 and December 2010, primary tumor tissue samples were collected from 234 subjects, including 107 triple-negative and 127 triple-positive breast cancer patients. The samples were embedded in paraffin and immunohistochemical staining was conducted to determine the expression levels of ERβ. The Kaplan-Meier method was used to analyze patient survival rates. ERβ expression was observed in 38/107 patients (35.5%) with triple-negative breast cancer and 63/127 patients (49.6%) with triple-positive breast cancer. The ERβ expression rate was significantly decreased in the patients with triple-negative breast cancer, as compared with those with triple-positive breast cancer (P=0.03). Analysis of the survival rates indicated that patients with triple-negative breast cancer and positive ERβ expression exhibited poor disease progression-free survival (DFS) compared with those with negative ERβ expression (P=0.021). However, no statistically significant difference was observed in the DFS between the triple-positive breast cancer patients with positive and negative ERβ expression. Therefore, the expression of ERβ varies between triple-negative and triple-positive breast cancer patients. In addition, positive expression of ERβ indicates a poor prognosis in triple-negative breast cancer patients; however, this is not the case for triple-positive breast cancer patients.