Phenotypic and Functional Characterization of Ductal Carcinoma In Situ-Associated Myoepithelial Cells

This study was undertaken to assess the characteristics of ductal carcinoma in situ (DCIS)-associated myoepithelial cells. Phenotypic and functional markers of myoepithelial cells were studied in pure DCIS, the DCIS component of infiltrating duct carcinoma (IDC), and adjacent normal breast tissue. There was decreased expression of myoepithelial cell markers in both groups of DCIS compared with normal breast tissue myoepithelial cells, suggesting that DCIS associated myoepithelial cells are phenotypically different from their normal counterparts. Background: Ductal carcinoma in situ (DCIS) is contained by myoepithelial cells that are morphologically similar to normal breast tissue myoepithelial cells. However, phenotypic and functional characteristics of DCIS-associated myoepithelial cells are not known. In this study, we aimed to assess the characteristics of DCIS-associated myoepithelial cells. Materials and Methods: lmmunophenotypic and functional characteristics of myoepithelial cells of pure DCIS, the DCIS component of infiltrating duct carcinoma (IDC), and the adjacent normal breast tissue of both groups (30 cases in each group) was assessed using phenotypic (CK5/6, CK14, p63, and calponin) and functional markers (maspin and CXCL14). Results: There was a decrease in expression of CK14, p63, and calponin in pure DCIS-associated myoepithelial cells compared with normal breast tissue myoepithelial cells (43.3% vs. 80.3%, 3.3% vs. 70%, 46.6 vs. 93.3%, respectively) and in the DCIS component of IDC compared with normal breast tissue myoepithelial cells (56.6% vs. 100%, 3.3% vs. 73.3%, 56.6% vs. 96.6%, respectively). CK5/6 expression was low to absent in myoepithelial cells of pure DCIS and the DCIS component of IDC as well as normal breast tissue myoepithelial cells. Maspin was expressed in all samples of normal breast tissue; however, 20% of pure DCIS and 26.6% of the DCIS component of IDC showed decreased expression. CXCL14 expression was greater in pure DCIS compared with adjacent normal breast tissue and the DCIS component of IDC. Conclusion: Decreased expression of myoepithelial cell markers in DCIS suggests that DCIS-associated myoepithelial cells are phenotypically different from their normal' counterparts. Two or more markers, preferably ID63 and calponin, should be used to distinguish in situ from invasive breast carcinomas.