Prediction of heterogeneity in breast cancer immunophenotype at ductal carcinoma in situ stage?

Introduction: Ductal carcinoma in situ (DCIS) is considered a heterogeneous lesion at the molecular level. However, there is a paucity of literature about the existence of molecular subtypes in DCIS which can predict their biological behavior at the preinvasive stage. Materials and Methods: Precise prevalence of molecular subtypes of pure DCIS and DCIS component of infiltrating duct carcinoma (IDC) was evaluated using immunohistochemistry and correlated with known prognostic factors. Results: DCIS cases were classified as luminal A (46.6% in each group), luminal B (pure DCIS 20% and DCIS component of IDC 13.3%), HER2 overexpressing, basal and nonbasal (pure DCIS 3.3% and 26.6% and DCIS component of IDC 3.3% and 33.3%, respectively), and triple negative, nonbasal (pure DCIS and DCIS component of IDC 3.3% each). The molecular phenotype of DCIS correlated well with that of the coexisting IDC. Conclusions: This study demonstrated molecular heterogeneity in DCIS; however, similar molecular phenotypes were seen in the coexisting IDC suggesting that DCIS is a precursor lesion and can predict phenotype of the invasive component. This also suggests that the invasiveness of DCIS is not dependent solely on the molecular character of the tumor epithelial cells, but factors such as tumor microenvironment may play a role.