SHORT REPORT Aldehyde dehydrogenase 1 expression predicts poor prognosis in triple-negative breast cancer Yasuyo Ohi, Yoshihisa Umekita, 1 Takako Yoshioka, 1 Masakazu Souda, 1 Yoshiaki Rai, Yoshiaki Sagara, Yasuaki Sagara, Yoshiatsu Sagara & Akihide Tanimoto 1 Hakuaikai Sagara Hospital and 1 Department of Molecular and Cellular Pathology, Field of Oncology, Kagoshima University, Graduate School of Medical and Dental Sciences, Kagoshima, Japan Date of submission 26 May 2010 Accepted for publication 23 November 2010 Ohi Y, Umekita Y, Yoshioka T, Souda M, Rai Y, Sagara Y, Sagara Y, Sagara Y & Tanimoto A (2011) Histopathology 59, 776–780 Aldehyde dehydrogenase 1 expression predicts poor prognosis in triple-negative breast cancer Aims: Aldehyde dehydrogenase 1 (ALDH1) has been identified as a reliable marker of breast cancer stem cells, and its clinical significance as a prognostic indicator of breast cancer has been reported by several investigators. However, the clinical significance of ALDH1 expression in triple-negative (TN) breast can- cer, a high-risk breast cancer lacking the benefit of specific therapy, remains to be solved. Methods and results: We performed immunohistochem- ical analyses of 106 TN breast cancers, using paraffin- embedded sections. The basal-like phenotype was also investigated with the use of basal cytokeratin 5 ⁄ 6 and epidermal growth factor receptor. ALDH1 expression in carcinoma cells was found in 59% of cases and was correlated with high histological grade alone (P < 0.006), whereas ALDH1 expression in stromal cells was found in 49% of cases but was not correlated with any clinicopathological parameter. Patients with ALDH1 expression in carcinoma cells had a shorter relapse-free survival (RFS) according to the log-rank test (P = 0.015). According to Cox multivariate anal- ysis, ALDH1 expression in carcinoma cells was an independent prognostic indicator of RFS (P = 0.025). The log-rank test revealed that stromal expression of ALDH1 had no effect on RFS. Conclusions: ALDH1 expression in carcinoma cells is an independent prognostic factor in TN breast cancer patients. Keywords: aldehyde dehydrogenase 1, immunohistochemistry, triple-negative breast cancer Abbreviations: ALDH1, aldehyde dehydrogenase 1; CK, cytokeratin; EGFR, epidermal growth factor receptor; IDC, invasive ductal carcinoma; RFS, relapse-free survival; TN, triple-negative Aldehyde dehydrogenase 1 (ALDH1) has been identi- fied as a reliable marker of breast cancer stem cells, and its clinical significance as a prognostic indicator of breast cancer has been reported by several investiga- tors. 1 Triple-negative (TN) breast cancer is a tumour subtype with aggressive clinical behaviour, for which there is currently a lack of effective targeted therapy. 2 In a recent long-term follow-up study, we found that ALDH1 expression in node-positive breast cancer patients predicted a poor prognosis. 3 We also found that TN breast cancer expressed ALDH1 more frequently than non-TN breast cancer. To date, only one study has investigated the clinical significance of Address for correspondence: A Tanimoto, MD, PhD, Department of Molecular and Cellular Pathology, Field of Oncology, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1, Sakuragaoka, Kagoshima 890-8544, Japan. e-mail: akit09@m3.kufm.kagoshima-u.ac.jp Y.O. and Y.U. contributed equally to this work. Ó 2011 Blackwell Publishing Limited. Histopathology 2011, 59, 776–780. DOI: 10.1111/j.1365-2559.2011.03884.x