ERBB2 and ductal breast carcinoma in situ: The staining intensity of POU2F3 was varied and stronger in one of the TNBC cases and in the luminal-HER2 case (Figs. 2 and 3) among the four cases; the strongest expression was observed in one of the TNBC cases reviewed in this study (i.e., with the DCIS component; Fig. 1).