Aberrant E-cadherin Expression in Invasive Ductal and Mixed Ductal-Lobular Breast Carcinomas

Loss of E-cadherin expression is a hallmark of invasive lobular carcinoma of the breast, whereas invasive ductal carcinoma (IDC) and mixed ductal-lobular carcinoma (MDLC) show heterogeneous expression patterns. This study aimed to quantitatively evaluate aberrant E-cadherin expression in IDC and MDLC and to assess its clinicopathological significance.

Immunohistochemistry for E-cadherin was performed in 47 IDC and 32 MDLC cases. Aberrant expression was defined as any of the following: non-classical membranous patterns (fragmented, focal, beaded, or weak), complete loss of membranous staining, or ectopic cytoplasmic/nuclear localization. For each case, the proportion of tumor area showing aberrant E-cadherin expression was quantified and correlated with clinicopathological parameters.

In IDC and MDLC, the optimal cutoff value for high aberrant E-cadherin expression was 30%, yielding the highest Youden index (0.264), with a sensitivity of 0.500 and specificity of 0.764. High aberrant E-cadherin expression was observed in 25 tumors (31.6%) and was significantly associated with larger tumor size (p=0.005) and lymph node metastasis (p=0.040).

A high proportion of aberrant E-cadherin expression is associated with aggressive clinicopathological features - including increased tumor size and lymph node metastasis - in IDC and MDLC. However, as it did not remain an independent predictor in multivariate analysis, its quantitative assessment may serve as a supplementary indicator of tumor aggressiveness rather than an independent prognostic marker, and further large-scale studies are required for validation.