Fig. 2: Intratumoral heterogeneity of HER2 expression.

A Homogeneous pattern: HER2-3+ case with nearly 100% tumor cells exhibiting diffuse strong positivity. B Clustering pattern: clear boundary between HER2-3+ and HER2-0 regions. C Mosaic pattern: clusters of HER2-3+ tumor cells in a HER2-2+ background. D Mosaic pattern: clusters of HER2-2+ tumor cells in a HER2-0 background. E Scattered pattern: isolated HER2-3+ tumor cells in a HER2-2+ background. F Scattered pattern: isolated HER2-3+ tumor cells in a HER2-0 background.