Distinct invasive patterns in situ between estrogen receptor‐positive and triple‐negative breast cancer through the intraductal tracking of carbon nanoparticles

Abstract Given that the transition from ductal carcinoma in situ (DCIS) to invasive breast cancer (BC) is crucial during the BC progression, the mechanism involved in the invasion transition behind triple‐negative breast cancer (TNBC) and estrogen receptor‐positive (ER‐positive) subtype has remained elusive. This article detected distinct invasion patterns of BC cells between the ER‐positive and TNBC using intraductal murine models with intraductal administration of carbon nanoparticles (CNPs). First, the feasibility of the utility of CNPs as a tracer was proved. The area ratio of CNPs and tumor cells invading the stroma at the late stage was found significantly higher than that in the early stage in MNU‐induced ER‐positive BC. However, opposite results were obtained in the triple‐negative model. Consequently, we proposed that the ER‐positive phenotype cells behave differently between different stages during tumor progression while there is no such difference in the invasion process of TNBC cells. The analysis regarding the duct integrity along with immunohistochemical characteristics further explained the distinct invasion features between the ER‐positive and triple‐negative subtypes. Last, the relationship between the duct thickness and the duct integrity suggested that ER‐positive tumors gradually increased in size within the lumen before the invasion. Overall, this study suggested the different invasion characteristics of ER‐positive BC and TNBC in vivo.