Characteristics of Invasive Micropapillary Carcinoma of the Breast: In Comparison with Invasive Ductal Carcinoma

Purpose: Invasive micropapillary carcinoma (IMPC) of the breast is a rare and associated with high incidence of lymph node metastasis and poor outcome. The aims of this study were to provide a comprehensive analysis of clinicopathologic and immunohistochemical characteristics of IMPC and to elucidate the differences between IMPC and invasive ductal carcinoma (IDC). Methods: Sixty-one patients of IMPC were identified by retrospective review of database from January 2004 to December 2008. 221 patients were randomly selected among the IDC patients who received operation during the same period. Two groups were compared with uni- and multivariate analysis. Results: We observed significant differences in mean number of metastatic lymph nodes (6.1 vs. 1.9, p=0.001), positivity of lymph node (70.5% vs. 45.2%, p<0.001), and presence of lymphatic vessel invasion (75.4% vs. 34.8%, p<0.001) between IMPC and IDC patients. Although it has been known that triple negative breast cancer (TNBC) have lymphotropic tendency in their early T stage, 11.8% (26/221) of IDC and 3.3% (2/61) of IMPC patients were TNBC in this study (p=0.050). In multivariate analysis, IMPC histology showed no correlation with disease-free survival (DFS) and the lymphatic vessel invasion was a significant predictor of DFS. Conclusion: The results of this study confirm that IMPC is unique subtype of breast cancer that is commonly accompanied by axillary lymph node metastasis and shows poor outcome, although it rarely presents the pattern of TNBC. Lymphatic vessel invasion rather than histology of IMPC seems to be more closely related to DFS.