RÉSUMÉ
To determine the role of E-cadherin in differentiating Breast lobular carcinoma from Breast ductal carcinoma in Iranian patients. A total of 80 malignant breast samples were reviewed by two pathologists before undergoing E-cad immunohistochemistry [IHC] staining. The results from IHC were compared with the results from the morphological study of the samples and they were then analyzed statistically. The normal ductal cells had strong complete homogenous membrane E-cadherin reactivity in all cases. The complete absence of E-cadherin membrane staining occurred in 14 out of 16 cases of Lobular breast carcinoma. The mean score of E-cadherin expression in ductal carcinoma was 191.35 with a CVof 104.39. In lobular carcinoma, the mean score of E-cadherin was 9.36 with a CV of 25.68. Using the Mann-Whiteny test, the difference between E-cadherin expression score in ductal and lobular carcinoma was statistically significant [P=0.0009]. E-cadherin expression is a useful diagnostic tool in distinguishing ductal from lobular carcinoma of breast