Objective To discuss the expression and mutation of β-catenin gene in breast carcinoma.Methods 119 breast carcinomas, 72 adenosis of breast tissues and 40 normal breast tissues were studied.Using immunohistochemistry studies to detect the expressions of β-catenin, then analyzing their relationship with the clinicopathological features of breast carcinomas. Gene mutation of β-catenin (exon 3) in 44 cases of breast carcinoma were analyzed by polymerase chain reaction (PCR) and then by direct sequencing.ResultsIn 40 cases of normal breast tissues, epithelial cells showed equally strong membranous of β-catenin protein at the cell-cell boundaries. The abnormal rate of β-catenin in breast carcinomas (78.15 %) was much higher than that of adenosis of breast tissues (44.44 %), the significant correlation was found (P＜0.01). The abnormal expression of β-catenin was associated with lymph node metastasis (P=0.031). Mutation of β-catenin gene was not detected in 44 cases of breast carcinoma, while the abnormal rate of β-catenin in 44 cases of breast carcinoma was 77.30 %. Conclusionβ-catenin abnormal expression could be considered as an useful marker for determining metastasis and prognosis of human breast carcinoma and for guiding treatment. β-catenin abnormal expression is not caused by β-catenin gene mutation, maybe by other mechanisms. It needs further study.