According to the authors of the study, treating physicians requested HER2 imaging for the following reasons: (1) to differentiate between metastases of multiple primary tumors with one confirmed primary HER2-positive breast cancer and additional primary cancers that could be breast cancer with no or low HER2 expression or other primary malignancies; (2) to assess the HER2 status of lesions not accessible to biopsy or repeat biopsy; and (3) to assess the heterogeneity of patients’ inter- and intratumoral HER2 expression [55]. This evidence concerns the gene ERBB2 and breast cancer.