In contrast to ESR1 only being expressed in CTCs of very few patients, HER2 gene expression at BL was found in seven out of 26 patients that were clinically diagnosed with HR+ breast cancer (e.g. Patient #3, Figure 3A) or TNBC (Patient #8 and 33, Figure 4A and 4C). The gene discussed is ERBB2; the disease is breast cancer.