Upregulation of N-cadherin in epithelial tumor cells has been shown to contribute to the invasive/metastatic phenotype. It remains however to be determined whether N-cadherin is increased in human breast cancers with enhanced malignant potential. We examined a large number of invasive breast cancer specimens (n = 114) for N- and E-cadherin. These specimens compared invasive duct carcinomas (IDCs) of varying histologic grades with an aggressive subtype, invasive micropapillary carcinoma of the breast (MPAP), which has a high propensity for lymphatic invasion and lymph node metastasis. Staining scores for N- and E-cadherin were compared between non-MPAP and MPAP IDCs, and between the invasive and ductal carcinoma in situ (DCIS) of each IDC using statistical analysis. We found that N-cadherin was expressed in 76% of MPAP and 52% of non-MPAP carcinomas, and E-cadherin in 57% of MPAP and 36% of non-MPAP tumors. More MPAP (25%) compared to non-MPAP (5%) tumors expressed both cadherins. Of the two cadherins, N-cadherin was significantly associated with MPAP tumors (p = 0.033) compared to E-cad (p = 0.171). Moreover, in the majority of tumors that were positive for N-cadherin, the staining scores were increased in the IDC relative to intraductal components, and this effect was more dramatic in the MPAP carcinomas. This difference for N-cadherin was greater than the corresponding difference for E-cadherin in the MPAP group (p = 0.005), whereas such changes were not significant in the non-MPAP group (p = 0.10). Thus, N-cadherin is associated with tumor aggressiveness and metastatic potential and may contribute to tumor progression.