ERBB2 and cancer: Microscopic analysis showed that the histopathology of HER2+/BL-ΔP tumors (n=15) was markedly different from that of HER2+/BL-wt tumors (n=8) (Figure 3A-J): the proportion of multilobular nodules was increased from 42% to 90% (Figure 3B,C); signs of minimal to moderate epithelial-mesenchymal transition (EMT; based on the cell morphology) were present in 93% of HER2+/BL-ΔP tumors, but absent in HER2+/BL-wt tumors (Figure 3A,D,E,F,G); and cancer cell embolization in vessels was detected in 46% of HER2+/BL-ΔP tumors, but absent in HER2+/BL-wt tumors (Figure 3A,H).