ObjectiveTo study the cause of different prognosis in typical medullary carcinoma and atypical medullary carcinoma. MethodsThe immunohistochemical staining method was used to evaluate the positivity of Ecadherin,βcatenin, in 30 cases of atypical medullary carcinoma and 18 cases of typical medullary carcinoma and 10 cases of normal breast. ResultsThe positive rate and staining intensity of Ecadherin and βcatenin oncoprotein were significantly higher in typical medullary carcinoma than in atypical medullary carcinoma(Plt;0.01).ConclusionExpression of Ecadherin and βcatenin is one of the causes of similar morphology and different prognosis in medullary breast carcinoma.