With the object of improving the assessment of the individual HER2 ITH in tumor samples, Nitta and colleagues, elaborated and validated a protocol in FFPE xenograft tumor tissue sections and in FFPE BC tissue-microarray (TMA) slides, that allows simultaneous brightfield-microscopy detection of HER2 protein and HER2 gene expression, called first tricolor HER2 gene-protein assay (GPA) (82). The gene discussed is ERBB2; the disease is neoplasm.