['The aim of this study was to investigate the expression of redox proteins in triple-negative breast cancer (TNBC), a breast cancer type which harbors an aggressive phenotype, and to demonstrate the relationships between the expression of reactive oxygen species (ROS) markers and clinical outcome.', 'From 2000 to 2005, we analyzed tissue samples from 135 cases of TNBC obtained from curative surgeries at the Severance Hospital, Seoul, South Korea. Immunochemical staining for redox proteins was performed.', 'The median patient age was 48 (range 27-76) years. TNM staging was as follows: T1 (n = 52, 38.5%), T2 (n = 81, 60%), T3 (n = 2, 1.5%), N0 (n = 88, 65.2%), N1 (n = 35, 25.9%), N2 (n = 8, 5.9%) and N3 (n = 4, 3.0%). Median follow-up was 59 (range 12-99) months. The high-expression catalase group tended to have a lower N stage (p = 0.016), lower tumor recurrence (p = 0.02) as well as longer overall survival rates (p = 0.05). After adjusting for patient age as well as tumor and nodal stage, we found that primary breast cancers with high catalase expression levels did not have an improved clinical outcome. A high MTC4 expression in the stroma was strongly associated with increased manganese superoxide dismutase expression (p = 0.015) and a significantly longer overall survival (p = 0.032).'] Is overexpression of reactive oxygen species scavenger enzymes associated with a good prognosis in triple-negative breast cancer?