ALDH1 expression is enriched in breast cancers arising in young women but does not predict outcome

BACKGROUND: Tumours arising in younger women appear to be biologically more aggressive and tend to have a poorer outcome. Being relatively resistant to conventional treatments, breast cancer stem cells (CSCs) have been postulated as a possible cause of disease recurrence after treatment. In this study, we used ALDH1 as a CSC marker and determined whether ALDH1 expression correlated with clinical outcome in young women with breast cancer. METHODS: The expression of ALDH1 was evaluated through immunohistochemistry on microarrayed cores obtained from 141 consecutive patients up to 35 years of age. RESULTS: The expression of ALDH1 was observed in 25% (35 of 141) of tumours, in a median of 5% of cells. Younger women were 14 times more likely to have ALDH1-positive tumours (P<0.01, OR 14.4, 95% CI 4.34–48.09). The ALDH1 correlated independently with ER negativity (P=0.01, OR 0.33, 95% CI 0.15–0.77). There was no correlation with disease recurrence or breast cancer-related deaths. CONCLUSION: In younger women, ALDH1 was more highly expressed, and it correlated with ER negativity. It, however, did not predict survival in this study.