['To investigate whether metastasis associated in colon cancer 1 (MACC1) expression is a prognostic marker in breast cancer and to demonstrate the potential correlation between MACC1 and mitogen-activated protein kinase (MAPK) expression.', 'Immunohistochemical staining with anti-MACC1 and phospho-p44/42 MAPK antibodies was performed in 198 invasive breast carcinomas using tissue microarray.', 'Expression of MACC1 was detected in 109 (55.1%) of 198 invasive breast carcinomas. MACC1 expression was significantly higher in the metastatic relapse-positive group (87.8%, 36/41) than in the metastatic relapse-negative group (46.5%, 73/157) (p < 0.001). MACC1 expression was significantly correlated with phospho-p44/42 MAPK expression (p < 0.05). On univariate analysis a significant association was observed between MACC1 expression and decreased disease-free survival (p < 0.001) and overall survival (p = 0.001). On multivariate analysis MACC1 expression was one of the statistically significant independent risk factors for disease-free survival (p = 0.001).'] Does metastasis associated in colon cancer 1 predict poor outcomes in patients with breast cancer?