The development of tissue microarray (TMA) technology has provided the opportunity to perform analyses of tissue samples on a large scale in an uniform fashion. This study was designed with the use of TMA to explore the Yes-associated protein (YAP) status in breast cancer.YAP expression in tumor and tumor-free samples from 94 patients with primary breast cancer was analyzed by TMA. The clinicopathological data for age, estrogen receptor status, histological grading and TNM staging were also collected.There were 29 patients (30.8%) with 1(+) expression, in YAP, 59 patients (62.8%) with 2(+) expression and 6 (6.4%) with 3(+) expression. There was no significant relationship between YAP expression and the other clinicopathological variables. By multivariate analysis, YAP expression failed to produce any significant relationship with the overall survival rate.YAP expression is not an independent prognostic factor in patients with breast cancer.