Two types of breast cancer treatment that are not included in the Guideline are relevant for fertility preservation: hormone therapy, namely tamoxifen (standard duration of therapy: 5–10 years), and anti-HER2 antibodies, e.g., with pertuzumab, trastuzumab and trastuzumab emtansine (standard duration of therapy: 1 year) [2, 7]. The gene discussed is ERBB2; the disease is breast cancer.