Ubiquitously transcribed tetratricopeptide repeat, X chromosome (UTX) is involved in the epigenetic regulation. A previous mouse xenograft study revealed that UTX knockdown is associated with downregulated expression of matrix metalloproteinase-11 (MMP-11). The authors investigated 224 cases of breast cancer from Kangbuk Samsung Medical Center between 2000 and 2005. Nuclear UTX and cytoplasmic MMP-11 expressions were assessed using immunohistochemistry of tumor tissue microarray specimens. The relationships between the expression of UTX, MMP-11, and patients' outcomes were analyzed. UTX expression was significantly associated with high histologic grade, lymphatic invasion, vascular invasion, and tumoral expression of MMP-11. Survival analysis revealed that patients with UTX expression had a poorer overall survival rate (P=0.010) as well as diminished disease-free survival rate (P=0.001). The prognostic power of UTX expression was significant in patients with luminal-type breast cancer (P=0.027, overall survival; P=0.008, disease-free survival). Validation of UTX can provide further prognostic information beyond traditional indicators and represents a potential therapeutic target for breast cancer.