Emerging evidence has shown that intratumoral HER2 heterogeneity (so-called ITH-HER2), currently defined by the presence of HER2 positivity in between 5 and 50% of tumor cells or the presence of an area of tumor testing HER2-negative, is a strong predictor of treatment response in HER2-positive patients10–14. Here, ERBB2 is linked to neoplasm.