Aim: To evaluate E-cadherin expression in various clinical and pathological prognostic scenarios to determine its significance in the development of molecular subtypes of invasive ductal breast cancer. Materials and Methods: A comprehensive morphological and immunohistochemical study of 80 cases of invasive ductal carcinoma (IDC) was conducted to determine the molecular phenotype. The expression of E-cadherin, ER, PR receptors, c-erbB2, and Ki-67 was evaluated according to the manufacturer’s standardized protocols using appropriate positive and negative controls. The degree of tumor malignancy was determined using the modified Scarff-Bloom- Richardson system. Semi-quantitative assessment of E-cadherin expression was performed using the Qureshi scale. Pearson’s criterion was used for statistical analysis. Differences were considered statistically significant at p < 0.05. Results: Low E-cadherin expression was associated with stage 3, pT3, and G2/G3 grades of IDBC malignancy, confirming its unfavorable prognostic significanc and correlation with the molecular profile. High E-cadherin expression was characteristic of ER-positive luminal A tumors, regardless of menopause, indicating a regulatory role for ER expression. The low proliferative activity of luminal IDBC cells was explained by high E-cadherin expression, which increased adhesive properties. Low E-cadherin expression is also a prognostic marker for TNBC. Conclusions: E-cadherin is a potent tumor suppressor in breast cancer. Its role in disease progression is confirmed by the correlation between partial or complete loss of E-cadherin expression and poor prognosis for patients.