Triple-negative breast carcinoma in women from Vietnam and the United States: characterization of differential marker expression by tissue microarray.

Triple-negative breast carcinoma accounts for approximately 15% of all breast cancers. It is characterized by an aggressive clinical history, high rate of local relapse, and association with the basal epithelial-like subtype. Variations in breast cancer subtype and clinical outcome often exist across racial and ethnic lines. Therefore, the aim of this study was to compare the immunohistochemical and clinicopathologic characteristics of triple-negative breast carcinoma in women living in Vietnam with those from the United States. Invasive triple-negative breast carcinoma of patients from the 2 populations was characterized by tissue microarray for the expression of basal cytokeratins (CK5/6, CK7, CK14), luminal cytokeratins (CK8, CK18, CK19), and markers associated with the basal phenotype (cKit, epithelial growth factor receptor, P-cadherin, p53, and p63). Significant differences in expression between the 2 populations were not observed for the basal cytokeratins. However, epithelial growth factor receptor and P-cadherin, markers associated with the basal phenotype, were underexpressed in Vietnamese patients. Of the luminal cytokeratins, CK8 was overexpressed and CK18 was underexpressed in the Vietnamese women. Significant differences were also observed regarding the clinicopathologic characteristics. Triple-negative breast carcinoma in Vietnamese women was smaller and less likely to be grade III. In addition, it was more frequently of ductal histologic type and less often medullary or metaplastic. These differences in histology and marker expression suggest that triple-negative breast carcinoma has unique biological characteristics in women from Vietnam and the United States, and may follow a unique clinical course in each of the 2 populations.