Abstract P6-01-04: Ductal Carcinoma In-Situ Associated with Triple-Negative Invasive Breast Carcinoma Is Often Immunohistochemically Distinct from Invasive Component

Abstract

Abstract Background: Gene expression profiling studies have identified a sub-set of breast carcinoma known as basal-like carcinoma, which characteristically do not express estrogen receptor (ER), progesterone receptor (PR), or HER2neu (HER2). These triple negative invasive ductal carcinomas (TN-IDC) are associated with an aggressive clinical course and poor prognosis. Little information exists in the literature concerning ductal carcinoma in-situ (DCIS) associated with TN-IDC. We evaluated the frequency, histologic features, and receptor status of DCIS associated with TN-IDC. Design: From our institutional archives between July 2006 and August 2009, we retrieved all cases of intermediate and high grade invasive ductal breast carcinoma. Based on the immunoprofiling, invasive carcinomas were categorized into either TN-IDC or non triple-negative invasive carcinoma (non-TN-IDC). Immunohistochemistry for ER, PR, and HER2 was performed on the DCIS of the TN-IDC group and on some available cases from the non-TN-IDC group. The frequency, receptor status, and nuclear grade of DCIS associated with both groups were noted. Statistical analysis was performed using Fisher Exact Test. Results: Among a total of 224 cases, 56 (25%) were classified as TN-IDC and 168 (75%) as non-TN-IDC. DCIS was seen in 28 (50%) TN-IDC cases and in 150 (89.3%) non-TN-IDC cases (P<0.0001). Sufficient tumor was available for immunohistochemical staining in 23 of 28 cases with DCIS in the TN-IDC group. Within the 23 cases, the DCIS were triple negative in 15 cases (65%). Of the remaining 8 cases (35%), 4 were positive for ER and PR, but negative for HER2, while the other 4 cases were negative for ER and PR but positive for HER2. Ninety-six cases in the non-TN-IDC group had available immunostains for review, 7 of which (7.3%) displayed a different receptor status from their invasive counterparts (p=0.0016, compared with TN-IDC). Two cases of non-TN-IDC showed an associated TN-DCIS. Of the 28 cases of TN-IDC associated with DCIS, 4 (14.3%) showed lower nuclear grade in DCIS than in its invasive counterpart, compared with 22 of 150 (14.7%) non-TN-IDC cases (no significant difference). One TN-IDC case displayed two distinct morphologic patterns of DCIS; neither pattern was triple negative. Conclusion: Our study demonstrated the presence of DCIS in a considerable proportion of TN-IDC although at a significantly lower frequency than in non-TN-IDC. DCIS associated with TN-IDC was significantly more likely to display a different immunoprofile from its invasive counterpart than DCIS associated with non-TN-IDC. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-01-04.